Logo Search packages:      
Sourcecode: linux-2.6 version File versions  Download package

ide-tape.c

/*
 * linux/drivers/ide/ide-tape.c           Version 1.19      Nov, 2003
 *
 * Copyright (C) 1995 - 1999 Gadi Oxman <gadio@netvision.net.il>
 *
 * $Header$
 *
 * This driver was constructed as a student project in the software laboratory
 * of the faculty of electrical engineering in the Technion - Israel's
 * Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David.
 *
 * It is hereby placed under the terms of the GNU general public license.
 * (See linux/COPYING).
 */
 
/*
 * IDE ATAPI streaming tape driver.
 *
 * This driver is a part of the Linux ide driver and works in co-operation
 * with linux/drivers/block/ide.c.
 *
 * The driver, in co-operation with ide.c, basically traverses the 
 * request-list for the block device interface. The character device
 * interface, on the other hand, creates new requests, adds them
 * to the request-list of the block device, and waits for their completion.
 *
 * Pipelined operation mode is now supported on both reads and writes.
 *
 * The block device major and minor numbers are determined from the
 * tape's relative position in the ide interfaces, as explained in ide.c.
 *
 * The character device interface consists of the following devices:
 *
 * ht0            major 37, minor 0 first  IDE tape, rewind on close.
 * ht1            major 37, minor 1 second IDE tape, rewind on close.
 * ...
 * nht0           major 37, minor 128     first  IDE tape, no rewind on close.
 * nht1           major 37, minor 129     second IDE tape, no rewind on close.
 * ...
 *
 * Run linux/scripts/MAKEDEV.ide to create the above entries.
 *
 * The general magnetic tape commands compatible interface, as defined by
 * include/linux/mtio.h, is accessible through the character device.
 *
 * General ide driver configuration options, such as the interrupt-unmask
 * flag, can be configured by issuing an ioctl to the block device interface,
 * as any other ide device.
 *
 * Our own ide-tape ioctl's can be issued to either the block device or
 * the character device interface.
 *
 * Maximal throughput with minimal bus load will usually be achieved in the
 * following scenario:
 *
 *    1.    ide-tape is operating in the pipelined operation mode.
 *    2.    No buffering is performed by the user backup program.
 *
 * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
 * 
 * Ver 0.1   Nov  1 95   Pre-working code :-)
 * Ver 0.2   Nov 23 95   A short backup (few megabytes) and restore procedure
 *                        was successful ! (Using tar cvf ... on the block
 *                        device interface).
 *                       A longer backup resulted in major swapping, bad
 *                        overall Linux performance and eventually failed as
 *                        we received non serial read-ahead requests from the
 *                        buffer cache.
 * Ver 0.3   Nov 28 95   Long backups are now possible, thanks to the
 *                        character device interface. Linux's responsiveness
 *                        and performance doesn't seem to be much affected
 *                        from the background backup procedure.
 *                       Some general mtio.h magnetic tape operations are
 *                        now supported by our character device. As a result,
 *                        popular tape utilities are starting to work with
 *                        ide tapes :-)
 *                       The following configurations were tested:
 *                            1. An IDE ATAPI TAPE shares the same interface
 *                               and irq with an IDE ATAPI CDROM.
 *                            2. An IDE ATAPI TAPE shares the same interface
 *                               and irq with a normal IDE disk.
 *                        Both configurations seemed to work just fine !
 *                        However, to be on the safe side, it is meanwhile
 *                        recommended to give the IDE TAPE its own interface
 *                        and irq.
 *                       The one thing which needs to be done here is to
 *                        add a "request postpone" feature to ide.c,
 *                        so that we won't have to wait for the tape to finish
 *                        performing a long media access (DSC) request (such
 *                        as a rewind) before we can access the other device
 *                        on the same interface. This effect doesn't disturb
 *                        normal operation most of the time because read/write
 *                        requests are relatively fast, and once we are
 *                        performing one tape r/w request, a lot of requests
 *                        from the other device can be queued and ide.c will
 *                  service all of them after this single tape request.
 * Ver 1.0   Dec 11 95   Integrated into Linux 1.3.46 development tree.
 *                       On each read / write request, we now ask the drive
 *                        if we can transfer a constant number of bytes
 *                        (a parameter of the drive) only to its buffers,
 *                        without causing actual media access. If we can't,
 *                        we just wait until we can by polling the DSC bit.
 *                        This ensures that while we are not transferring
 *                        more bytes than the constant referred to above, the
 *                        interrupt latency will not become too high and
 *                        we won't cause an interrupt timeout, as happened
 *                        occasionally in the previous version.
 *                       While polling for DSC, the current request is
 *                        postponed and ide.c is free to handle requests from
 *                        the other device. This is handled transparently to
 *                        ide.c. The hwgroup locking method which was used
 *                        in the previous version was removed.
 *                       Use of new general features which are provided by
 *                        ide.c for use with atapi devices.
 *                        (Programming done by Mark Lord)
 *                       Few potential bug fixes (Again, suggested by Mark)
 *                       Single character device data transfers are now
 *                        not limited in size, as they were before.
 *                       We are asking the tape about its recommended
 *                        transfer unit and send a larger data transfer
 *                        as several transfers of the above size.
 *                        For best results, use an integral number of this
 *                        basic unit (which is shown during driver
 *                        initialization). I will soon add an ioctl to get
 *                        this important parameter.
 *                       Our data transfer buffer is allocated on startup,
 *                        rather than before each data transfer. This should
 *                        ensure that we will indeed have a data buffer.
 * Ver 1.1   Dec 14 95   Fixed random problems which occurred when the tape
 *                        shared an interface with another device.
 *                        (poll_for_dsc was a complete mess).
 *                       Removed some old (non-active) code which had
 *                        to do with supporting buffer cache originated
 *                        requests.
 *                       The block device interface can now be opened, so
 *                        that general ide driver features like the unmask
 *                        interrupts flag can be selected with an ioctl.
 *                        This is the only use of the block device interface.
 *                       New fast pipelined operation mode (currently only on
 *                        writes). When using the pipelined mode, the
 *                        throughput can potentially reach the maximum
 *                        tape supported throughput, regardless of the
 *                        user backup program. On my tape drive, it sometimes
 *                        boosted performance by a factor of 2. Pipelined
 *                        mode is enabled by default, but since it has a few
 *                        downfalls as well, you may want to disable it.
 *                        A short explanation of the pipelined operation mode
 *                        is available below.
 * Ver 1.2   Jan  1 96   Eliminated pipelined mode race condition.
 *                       Added pipeline read mode. As a result, restores
 *                        are now as fast as backups.
 *                       Optimized shared interface behavior. The new behavior
 *                        typically results in better IDE bus efficiency and
 *                        higher tape throughput.
 *                       Pre-calculation of the expected read/write request
 *                        service time, based on the tape's parameters. In
 *                        the pipelined operation mode, this allows us to
 *                        adjust our polling frequency to a much lower value,
 *                        and thus to dramatically reduce our load on Linux,
 *                        without any decrease in performance.
 *                       Implemented additional mtio.h operations.
 *                       The recommended user block size is returned by
 *                        the MTIOCGET ioctl.
 *                       Additional minor changes.
 * Ver 1.3   Feb  9 96   Fixed pipelined read mode bug which prevented the
 *                        use of some block sizes during a restore procedure.
 *                       The character device interface will now present a
 *                        continuous view of the media - any mix of block sizes
 *                        during a backup/restore procedure is supported. The
 *                        driver will buffer the requests internally and
 *                        convert them to the tape's recommended transfer
 *                        unit, making performance almost independent of the
 *                        chosen user block size.
 *                       Some improvements in error recovery.
 *                       By cooperating with ide-dma.c, bus mastering DMA can
 *                        now sometimes be used with IDE tape drives as well.
 *                        Bus mastering DMA has the potential to dramatically
 *                        reduce the CPU's overhead when accessing the device,
 *                        and can be enabled by using hdparm -d1 on the tape's
 *                        block device interface. For more info, read the
 *                        comments in ide-dma.c.
 * Ver 1.4   Mar 13 96   Fixed serialize support.
 * Ver 1.5   Apr 12 96   Fixed shared interface operation, broken in 1.3.85.
 *                       Fixed pipelined read mode inefficiency.
 *                       Fixed nasty null dereferencing bug.
 * Ver 1.6   Aug 16 96   Fixed FPU usage in the driver.
 *                       Fixed end of media bug.
 * Ver 1.7   Sep 10 96   Minor changes for the CONNER CTT8000-A model.
 * Ver 1.8   Sep 26 96   Attempt to find a better balance between good
 *                        interactive response and high system throughput.
 * Ver 1.9   Nov  5 96   Automatically cross encountered filemarks rather
 *                        than requiring an explicit FSF command.
 *                       Abort pending requests at end of media.
 *                       MTTELL was sometimes returning incorrect results.
 *                       Return the real block size in the MTIOCGET ioctl.
 *                       Some error recovery bug fixes.
 * Ver 1.10  Nov  5 96   Major reorganization.
 *                       Reduced CPU overhead a bit by eliminating internal
 *                        bounce buffers.
 *                       Added module support.
 *                       Added multiple tape drives support.
 *                       Added partition support.
 *                       Rewrote DSC handling.
 *                       Some portability fixes.
 *                       Removed ide-tape.h.
 *                       Additional minor changes.
 * Ver 1.11  Dec  2 96   Bug fix in previous DSC timeout handling.
 *                       Use ide_stall_queue() for DSC overlap.
 *                       Use the maximum speed rather than the current speed
 *                        to compute the request service time.
 * Ver 1.12  Dec  7 97   Fix random memory overwriting and/or last block data
 *                        corruption, which could occur if the total number
 *                        of bytes written to the tape was not an integral
 *                        number of tape blocks.
 *                       Add support for INTERRUPT DRQ devices.
 * Ver 1.13  Jan  2 98   Add "speed == 0" work-around for HP COLORADO 5GB
 * Ver 1.14  Dec 30 98   Partial fixes for the Sony/AIWA tape drives.
 *                       Replace cli()/sti() with hwgroup spinlocks.
 * Ver 1.15  Mar 25 99   Fix SMP race condition by replacing hwgroup
 *                        spinlock with private per-tape spinlock.
 * Ver 1.16  Sep  1 99   Add OnStream tape support.
 *                       Abort read pipeline on EOD.
 *                       Wait for the tape to become ready in case it returns
 *                        "in the process of becoming ready" on open().
 *                       Fix zero padding of the last written block in
 *                        case the tape block size is larger than PAGE_SIZE.
 *                       Decrease the default disconnection time to tn.
 * Ver 1.16e Oct  3 99   Minor fixes.
 * Ver 1.16e1 Oct 13 99  Patches by Arnold Niessen,
 *                          niessen@iae.nl / arnold.niessen@philips.com
 *                   GO-1)  Undefined code in idetape_read_position
 *                      according to Gadi's email
 *                   AJN-1) Minor fix asc == 11 should be asc == 0x11
 *                               in idetape_issue_packet_command (did effect
 *                               debugging output only)
 *                   AJN-2) Added more debugging output, and
 *                              added ide-tape: where missing. I would also
 *                      like to add tape->name where possible
 *                   AJN-3) Added different debug_level's 
 *                              via /proc/ide/hdc/settings
 *                      "debug_level" determines amount of debugging output;
 *                      can be changed using /proc/ide/hdx/settings
 *                      0 : almost no debugging output
 *                      1 : 0+output errors only
 *                      2 : 1+output all sensekey/asc
 *                      3 : 2+follow all chrdev related procedures
 *                      4 : 3+follow all procedures
 *                      5 : 4+include pc_stack rq_stack info
 *                      6 : 5+USE_COUNT updates
 *                   AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
 *                      from 5 to 10 minutes
 *                   AJN-5) Changed maximum number of blocks to skip when
 *                              reading tapes with multiple consecutive write
 *                              errors from 100 to 1000 in idetape_get_logical_blk
 *                   Proposed changes to code:
 *                   1) output "logical_blk_num" via /proc
 *                   2) output "current_operation" via /proc
 *                   3) Either solve or document the fact that `mt rewind' is
 *                      required after reading from /dev/nhtx to be
 *                able to rmmod the idetape module;
 *                Also, sometimes an application finishes but the
 *                device remains `busy' for some time. Same cause ?
 *                   Proposed changes to release-notes:
 *               4) write a simple `quickstart' section in the
 *                      release notes; I volunteer if you don't want to
 *               5) include a pointer to video4linux in the doc
 *                      to stimulate video applications
 *                   6) release notes lines 331 and 362: explain what happens
 *                if the application data rate is higher than 1100 KB/s; 
 *                similar approach to lower-than-500 kB/s ?
 *               7) 6.6 Comparison; wouldn't it be better to allow different 
 *                strategies for read and write ?
 *                Wouldn't it be better to control the tape buffer
 *                contents instead of the bandwidth ?
 *               8) line 536: replace will by would (if I understand
 *                this section correctly, a hypothetical and unwanted situation
 *                 is being described)
 * Ver 1.16f Dec 15 99   Change place of the secondary OnStream header frames.
 * Ver 1.17  Nov 2000 / Jan 2001  Marcel Mol, marcel@mesa.nl
 *                - Add idetape_onstream_mode_sense_tape_parameter_page
 *                  function to get tape capacity in frames: tape->capacity.
 *                - Add support for DI-50 drives( or any DI- drive).
 *                - 'workaround' for read error/blank block around block 3000.
 *                - Implement Early warning for end of media for Onstream.
 *                - Cosmetic code changes for readability.
 *                - Idetape_position_tape should not use SKIP bit during
 *                  Onstream read recovery.
 *                - Add capacity, logical_blk_num and first/last_frame_position
 *                  to /proc/ide/hd?/settings.
 *                - Module use count was gone in the Linux 2.4 driver.
 * Ver 1.17a Apr 2001 Willem Riede osst@riede.org
 *                - Get drive's actual block size from mode sense block descriptor
 *                - Limit size of pipeline
 * Ver 1.17b Oct 2002   Alan Stern <stern@rowland.harvard.edu>
 *                Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
 *                 it in the code!
 *                Actually removed aborted stages in idetape_abort_pipeline
 *                 instead of just changing the command code.
 *                Made the transfer byte count for Request Sense equal to the
 *                 actual length of the data transfer.
 *                Changed handling of partial data transfers: they do not
 *                 cause DMA errors.
 *                Moved initiation of DMA transfers to the correct place.
 *                Removed reference to unallocated memory.
 *                Made __idetape_discard_read_pipeline return the number of
 *                 sectors skipped, not the number of stages.
 *                Replaced errant kfree() calls with __idetape_kfree_stage().
 *                Fixed off-by-one error in testing the pipeline length.
 *                Fixed handling of filemarks in the read pipeline.
 *                Small code optimization for MTBSF and MTBSFM ioctls.
 *                Don't try to unlock the door during device close if is
 *                 already unlocked!
 *                Cosmetic fixes to miscellaneous debugging output messages.
 *                Set the minimum /proc/ide/hd?/settings values for "pipeline",
 *                 "pipeline_min", and "pipeline_max" to 1.
 *
 * Here are some words from the first releases of hd.c, which are quoted
 * in ide.c and apply here as well:
 *
 * | Special care is recommended.  Have Fun!
 *
 */

/*
 * An overview of the pipelined operation mode.
 *
 * In the pipelined write mode, we will usually just add requests to our
 * pipeline and return immediately, before we even start to service them. The
 * user program will then have enough time to prepare the next request while
 * we are still busy servicing previous requests. In the pipelined read mode,
 * the situation is similar - we add read-ahead requests into the pipeline,
 * before the user even requested them.
 *
 * The pipeline can be viewed as a "safety net" which will be activated when
 * the system load is high and prevents the user backup program from keeping up
 * with the current tape speed. At this point, the pipeline will get
 * shorter and shorter but the tape will still be streaming at the same speed.
 * Assuming we have enough pipeline stages, the system load will hopefully
 * decrease before the pipeline is completely empty, and the backup program
 * will be able to "catch up" and refill the pipeline again.
 * 
 * When using the pipelined mode, it would be best to disable any type of
 * buffering done by the user program, as ide-tape already provides all the
 * benefits in the kernel, where it can be done in a more efficient way.
 * As we will usually not block the user program on a request, the most
 * efficient user code will then be a simple read-write-read-... cycle.
 * Any additional logic will usually just slow down the backup process.
 *
 * Using the pipelined mode, I get a constant over 400 KBps throughput,
 * which seems to be the maximum throughput supported by my tape.
 *
 * However, there are some downfalls:
 *
 *    1.    We use memory (for data buffers) in proportional to the number
 *          of pipeline stages (each stage is about 26 KB with my tape).
 *    2.    In the pipelined write mode, we cheat and postpone error codes
 *          to the user task. In read mode, the actual tape position
 *          will be a bit further than the last requested block.
 *
 * Concerning (1):
 *
 *    1.    We allocate stages dynamically only when we need them. When
 *          we don't need them, we don't consume additional memory. In
 *          case we can't allocate stages, we just manage without them
 *          (at the expense of decreased throughput) so when Linux is
 *          tight in memory, we will not pose additional difficulties.
 *
 *    2.    The maximum number of stages (which is, in fact, the maximum
 *          amount of memory) which we allocate is limited by the compile
 *          time parameter IDETAPE_MAX_PIPELINE_STAGES.
 *
 *    3.    The maximum number of stages is a controlled parameter - We
 *          don't start from the user defined maximum number of stages
 *          but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
 *          will not even allocate this amount of stages if the user
 *          program can't handle the speed). We then implement a feedback
 *          loop which checks if the pipeline is empty, and if it is, we
 *          increase the maximum number of stages as necessary until we
 *          reach the optimum value which just manages to keep the tape
 *          busy with minimum allocated memory or until we reach
 *          IDETAPE_MAX_PIPELINE_STAGES.
 *
 * Concerning (2):
 *
 *    In pipelined write mode, ide-tape can not return accurate error codes
 *    to the user program since we usually just add the request to the
 *      pipeline without waiting for it to be serviced. In case an error
 *      occurs, I will report it on the next user request.
 *
 *    In the pipelined read mode, subsequent read requests or forward
 *    filemark spacing will perform correctly, as we preserve all blocks
 *    and filemarks which we encountered during our excess read-ahead.
 * 
 *    For accurate tape positioning and error reporting, disabling
 *    pipelined mode might be the best option.
 *
 * You can enable/disable/tune the pipelined operation mode by adjusting
 * the compile time parameters below.
 */

/*
 *    Possible improvements.
 *
 *    1.    Support for the ATAPI overlap protocol.
 *
 *          In order to maximize bus throughput, we currently use the DSC
 *          overlap method which enables ide.c to service requests from the
 *          other device while the tape is busy executing a command. The
 *          DSC overlap method involves polling the tape's status register
 *          for the DSC bit, and servicing the other device while the tape
 *          isn't ready.
 *
 *          In the current QIC development standard (December 1995),
 *          it is recommended that new tape drives will *in addition* 
 *          implement the ATAPI overlap protocol, which is used for the
 *          same purpose - efficient use of the IDE bus, but is interrupt
 *          driven and thus has much less CPU overhead.
 *
 *          ATAPI overlap is likely to be supported in most new ATAPI
 *          devices, including new ATAPI cdroms, and thus provides us
 *          a method by which we can achieve higher throughput when
 *          sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
 */

#define IDETAPE_VERSION "1.19"

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/ide.h>
#include <linux/smp_lock.h>
#include <linux/completion.h>
#include <linux/bitops.h>
#include <linux/mutex.h>

#include <asm/byteorder.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/unaligned.h>

/*
 * partition
 */
typedef struct os_partition_s {
      __u8  partition_num;
      __u8  par_desc_ver;
      __u16 wrt_pass_cntr;
      __u32 first_frame_addr;
      __u32 last_frame_addr;
      __u32 eod_frame_addr;
} os_partition_t;

/*
 * DAT entry
 */
typedef struct os_dat_entry_s {
      __u32 blk_sz;
      __u16 blk_cnt;
      __u8  flags;
      __u8  reserved;
} os_dat_entry_t;

/*
 * DAT
 */
#define OS_DAT_FLAGS_DATA     (0xc)
#define OS_DAT_FLAGS_MARK     (0x1)

typedef struct os_dat_s {
      __u8        dat_sz;
      __u8        reserved1;
      __u8        entry_cnt;
      __u8        reserved3;
      os_dat_entry_t    dat_list[16];
} os_dat_t;

#include <linux/mtio.h>

/**************************** Tunable parameters *****************************/


/*
 *    Pipelined mode parameters.
 *
 *    We try to use the minimum number of stages which is enough to
 *    keep the tape constantly streaming. To accomplish that, we implement
 *    a feedback loop around the maximum number of stages:
 *
 *    We start from MIN maximum stages (we will not even use MIN stages
 *      if we don't need them), increment it by RATE*(MAX-MIN)
 *    whenever we sense that the pipeline is empty, until we reach
 *    the optimum value or until we reach MAX.
 *
 *    Setting the following parameter to 0 is illegal: the pipelined mode
 *    cannot be disabled (calculate_speeds() divides by tape->max_stages.)
 */
#define IDETAPE_MIN_PIPELINE_STAGES   1
#define IDETAPE_MAX_PIPELINE_STAGES 400
#define IDETAPE_INCREASE_STAGES_RATE       20

/*
 *    The following are used to debug the driver:
 *
 *    Setting IDETAPE_DEBUG_INFO to 1 will report device capabilities.
 *    Setting IDETAPE_DEBUG_LOG to 1 will log driver flow control.
 *    Setting IDETAPE_DEBUG_BUGS to 1 will enable self-sanity checks in
 *    some places.
 *
 *    Setting them to 0 will restore normal operation mode:
 *
 *          1.    Disable logging normal successful operations.
 *          2.    Disable self-sanity checks.
 *          3.    Errors will still be logged, of course.
 *
 *    All the #if DEBUG code will be removed some day, when the driver
 *    is verified to be stable enough. This will make it much more
 *    esthetic.
 */
#define IDETAPE_DEBUG_INFO          0
#define IDETAPE_DEBUG_LOG           0
#define IDETAPE_DEBUG_BUGS          1

/*
 *    After each failed packet command we issue a request sense command
 *    and retry the packet command IDETAPE_MAX_PC_RETRIES times.
 *
 *    Setting IDETAPE_MAX_PC_RETRIES to 0 will disable retries.
 */
#define IDETAPE_MAX_PC_RETRIES            3

/*
 *    With each packet command, we allocate a buffer of
 *    IDETAPE_PC_BUFFER_SIZE bytes. This is used for several packet
 *    commands (Not for READ/WRITE commands).
 */
#define IDETAPE_PC_BUFFER_SIZE            256

/*
 *    In various places in the driver, we need to allocate storage
 *    for packet commands and requests, which will remain valid while
 *    we leave the driver to wait for an interrupt or a timeout event.
 */
#define IDETAPE_PC_STACK            (10 + IDETAPE_MAX_PC_RETRIES)

/*
 * Some drives (for example, Seagate STT3401A Travan) require a very long
 * timeout, because they don't return an interrupt or clear their busy bit
 * until after the command completes (even retension commands).
 */
#define IDETAPE_WAIT_CMD            (900*HZ)

/*
 *    The following parameter is used to select the point in the internal
 *    tape fifo in which we will start to refill the buffer. Decreasing
 *    the following parameter will improve the system's latency and
 *    interactive response, while using a high value might improve sytem
 *    throughput.
 */
#define IDETAPE_FIFO_THRESHOLD            2

/*
 *    DSC polling parameters.
 *
 *    Polling for DSC (a single bit in the status register) is a very
 *    important function in ide-tape. There are two cases in which we
 *    poll for DSC:
 *
 *    1.    Before a read/write packet command, to ensure that we
 *          can transfer data from/to the tape's data buffers, without
 *          causing an actual media access. In case the tape is not
 *          ready yet, we take out our request from the device
 *          request queue, so that ide.c will service requests from
 *          the other device on the same interface meanwhile.
 *
 *    2.    After the successful initialization of a "media access
 *          packet command", which is a command which can take a long
 *          time to complete (it can be several seconds or even an hour).
 *
 *          Again, we postpone our request in the middle to free the bus
 *          for the other device. The polling frequency here should be
 *          lower than the read/write frequency since those media access
 *          commands are slow. We start from a "fast" frequency -
 *          IDETAPE_DSC_MA_FAST (one second), and if we don't receive DSC
 *          after IDETAPE_DSC_MA_THRESHOLD (5 minutes), we switch it to a
 *          lower frequency - IDETAPE_DSC_MA_SLOW (1 minute).
 *
 *    We also set a timeout for the timer, in case something goes wrong.
 *    The timeout should be longer then the maximum execution time of a
 *    tape operation.
 */
 
/*
 *    DSC timings.
 */
#define IDETAPE_DSC_RW_MIN          5*HZ/100    /* 50 msec */
#define IDETAPE_DSC_RW_MAX          40*HZ/100   /* 400 msec */
#define IDETAPE_DSC_RW_TIMEOUT            2*60*HZ           /* 2 minutes */
#define IDETAPE_DSC_MA_FAST         2*HZ        /* 2 seconds */
#define IDETAPE_DSC_MA_THRESHOLD    5*60*HZ           /* 5 minutes */
#define IDETAPE_DSC_MA_SLOW         30*HZ       /* 30 seconds */
#define IDETAPE_DSC_MA_TIMEOUT            2*60*60*HZ  /* 2 hours */

/*************************** End of tunable parameters ***********************/

/*
 *    Debugging/Performance analysis
 *
 *    I/O trace support
 */
#define USE_IOTRACE     0
#if USE_IOTRACE
#include <linux/io_trace.h>
#define IO_IDETAPE_FIFO 500
#endif

/*
 *    Read/Write error simulation
 */
#define SIMULATE_ERRORS             0

/*
 *    For general magnetic tape device compatibility.
 */
typedef enum {
      idetape_direction_none,
      idetape_direction_read,
      idetape_direction_write
} idetape_chrdev_direction_t;

struct idetape_bh {
      unsigned short b_size;
      atomic_t b_count;
      struct idetape_bh *b_reqnext;
      char *b_data;
};

/*
 *    Our view of a packet command.
 */
typedef struct idetape_packet_command_s {
      u8 c[12];                     /* Actual packet bytes */
      int retries;                        /* On each retry, we increment retries */
      int error;                    /* Error code */
      int request_transfer;               /* Bytes to transfer */
      int actually_transferred;           /* Bytes actually transferred */
      int buffer_size;              /* Size of our data buffer */
      struct idetape_bh *bh;
      char *b_data;
      int b_count;
      u8 *buffer;                   /* Data buffer */
      u8 *current_position;               /* Pointer into the above buffer */
      ide_startstop_t (*callback) (ide_drive_t *);    /* Called when this packet command is completed */
      u8 pc_buffer[IDETAPE_PC_BUFFER_SIZE];     /* Temporary buffer */
      unsigned long flags;                /* Status/Action bit flags: long for set_bit */
} idetape_pc_t;

/*
 *    Packet command flag bits.
 */
/* Set when an error is considered normal - We won't retry */
#define     PC_ABORT                0
/* 1 When polling for DSC on a media access command */
#define PC_WAIT_FOR_DSC             1
/* 1 when we prefer to use DMA if possible */
#define PC_DMA_RECOMMENDED          2
/* 1 while DMA in progress */
#define     PC_DMA_IN_PROGRESS            3
/* 1 when encountered problem during DMA */
#define     PC_DMA_ERROR                  4
/* Data direction */
#define     PC_WRITING              5

/*
 *    Capabilities and Mechanical Status Page
 */
typedef struct {
      unsigned    page_code   :6;   /* Page code - Should be 0x2a */
      __u8        reserved0_6 :1;
      __u8        ps          :1;   /* parameters saveable */
      __u8        page_length;            /* Page Length - Should be 0x12 */
      __u8        reserved2, reserved3;
      unsigned    ro          :1;   /* Read Only Mode */
      unsigned    reserved4_1234    :4;
      unsigned    sprev       :1;   /* Supports SPACE in the reverse direction */
      unsigned    reserved4_67      :2;
      unsigned    reserved5_012     :3;
      unsigned    efmt        :1;   /* Supports ERASE command initiated formatting */
      unsigned    reserved5_4 :1;
      unsigned    qfa         :1;   /* Supports the QFA two partition formats */
      unsigned    reserved5_67      :2;
      unsigned    lock        :1;   /* Supports locking the volume */
      unsigned    locked            :1;   /* The volume is locked */
      unsigned    prevent           :1;   /* The device defaults in the prevent state after power up */     
      unsigned    eject       :1;   /* The device can eject the volume */
      __u8        disconnect  :1;   /* The device can break request > ctl */  
      __u8        reserved6_5 :1;
      unsigned    ecc         :1;   /* Supports error correction */
      unsigned    cmprs       :1;   /* Supports data compression */
      unsigned    reserved7_0 :1;
      unsigned    blk512            :1;   /* Supports 512 bytes block size */
      unsigned    blk1024           :1;   /* Supports 1024 bytes block size */
      unsigned    reserved7_3_6     :4;
      unsigned    blk32768    :1;   /* slowb - the device restricts the byte count for PIO */
                                    /* transfers for slow buffer memory ??? */
                                    /* Also 32768 block size in some cases */
      __u16       max_speed;        /* Maximum speed supported in KBps */
      __u8        reserved10, reserved11;
      __u16       ctl;              /* Continuous Transfer Limit in blocks */
      __u16       speed;                  /* Current Speed, in KBps */
      __u16       buffer_size;            /* Buffer Size, in 512 bytes */
      __u8        reserved18, reserved19;
} idetape_capabilities_page_t;

/*
 *    Block Size Page
 */
typedef struct {
      unsigned    page_code   :6;   /* Page code - Should be 0x30 */
      unsigned    reserved1_6 :1;
      unsigned    ps          :1;
      __u8        page_length;            /* Page Length - Should be 2 */
      __u8        reserved2;
      unsigned    play32            :1;
      unsigned    play32_5    :1;
      unsigned    reserved2_23      :2;
      unsigned    record32    :1;
      unsigned    record32_5  :1;
      unsigned    reserved2_6 :1;
      unsigned    one         :1;
} idetape_block_size_page_t;

/*
 *    A pipeline stage.
 */
typedef struct idetape_stage_s {
      struct request rq;                  /* The corresponding request */
      struct idetape_bh *bh;              /* The data buffers */
      struct idetape_stage_s *next;       /* Pointer to the next stage */
} idetape_stage_t;

/*
 *    REQUEST SENSE packet command result - Data Format.
 */
typedef struct {
      unsigned    error_code  :7;   /* Current of deferred errors */
      unsigned    valid       :1;   /* The information field conforms to QIC-157C */
      __u8        reserved1   :8;   /* Segment Number - Reserved */
      unsigned    sense_key   :4;   /* Sense Key */
      unsigned    reserved2_4 :1;   /* Reserved */
      unsigned    ili         :1;   /* Incorrect Length Indicator */
      unsigned    eom         :1;   /* End Of Medium */
      unsigned    filemark    :1;   /* Filemark */
      __u32       information __attribute__ ((packed));
      __u8        asl;              /* Additional sense length (n-7) */
      __u32       command_specific; /* Additional command specific information */
      __u8        asc;              /* Additional Sense Code */
      __u8        ascq;             /* Additional Sense Code Qualifier */
      __u8        replaceable_unit_code;  /* Field Replaceable Unit Code */
      unsigned    sk_specific1      :7;   /* Sense Key Specific */
      unsigned    sksv        :1;   /* Sense Key Specific information is valid */
      __u8        sk_specific2;           /* Sense Key Specific */
      __u8        sk_specific3;           /* Sense Key Specific */
      __u8        pad[2];                 /* Padding to 20 bytes */
} idetape_request_sense_result_t;


/*
 *    Most of our global data which we need to save even as we leave the
 *    driver due to an interrupt or a timer event is stored in a variable
 *    of type idetape_tape_t, defined below.
 */
typedef struct ide_tape_obj {
      ide_drive_t *drive;
      ide_driver_t      *driver;
      struct gendisk    *disk;
      struct kref kref;

      /*
       *    Since a typical character device operation requires more
       *    than one packet command, we provide here enough memory
       *    for the maximum of interconnected packet commands.
       *    The packet commands are stored in the circular array pc_stack.
       *    pc_stack_index points to the last used entry, and warps around
       *    to the start when we get to the last array entry.
       *
       *    pc points to the current processed packet command.
       *
       *    failed_pc points to the last failed packet command, or contains
       *    NULL if we do not need to retry any packet command. This is
       *    required since an additional packet command is needed before the
       *    retry, to get detailed information on what went wrong.
       */
      /* Current packet command */
      idetape_pc_t *pc;
      /* Last failed packet command */
      idetape_pc_t *failed_pc;
      /* Packet command stack */
      idetape_pc_t pc_stack[IDETAPE_PC_STACK];
      /* Next free packet command storage space */
      int pc_stack_index;
      struct request rq_stack[IDETAPE_PC_STACK];
      /* We implement a circular array */
      int rq_stack_index;

      /*
       *    DSC polling variables.
       *
       *    While polling for DSC we use postponed_rq to postpone the
       *    current request so that ide.c will be able to service
       *    pending requests on the other device. Note that at most
       *    we will have only one DSC (usually data transfer) request
       *    in the device request queue. Additional requests can be
       *    queued in our internal pipeline, but they will be visible
       *    to ide.c only one at a time.
       */
      struct request *postponed_rq;
      /* The time in which we started polling for DSC */
      unsigned long dsc_polling_start;
      /* Timer used to poll for dsc */
      struct timer_list dsc_timer;
      /* Read/Write dsc polling frequency */
      unsigned long best_dsc_rw_frequency;
      /* The current polling frequency */
      unsigned long dsc_polling_frequency;
      /* Maximum waiting time */
      unsigned long dsc_timeout;

      /*
       *    Read position information
       */
      u8 partition;
      /* Current block */
      unsigned int first_frame_position;
      unsigned int last_frame_position;
      unsigned int blocks_in_buffer;

      /*
       *    Last error information
       */
      u8 sense_key, asc, ascq;

      /*
       *    Character device operation
       */
      unsigned int minor;
      /* device name */
      char name[4];
      /* Current character device data transfer direction */
      idetape_chrdev_direction_t chrdev_direction;

      /*
       *    Device information
       */
      /* Usually 512 or 1024 bytes */
      unsigned short tape_block_size;
      int user_bs_factor;
      /* Copy of the tape's Capabilities and Mechanical Page */
      idetape_capabilities_page_t capabilities;

      /*
       *    Active data transfer request parameters.
       *
       *    At most, there is only one ide-tape originated data transfer
       *    request in the device request queue. This allows ide.c to
       *    easily service requests from the other device when we
       *    postpone our active request. In the pipelined operation
       *    mode, we use our internal pipeline structure to hold
       *    more data requests.
       *
       *    The data buffer size is chosen based on the tape's
       *    recommendation.
       */
      /* Pointer to the request which is waiting in the device request queue */
      struct request *active_data_request;
      /* Data buffer size (chosen based on the tape's recommendation */
      int stage_size;
      idetape_stage_t *merge_stage;
      int merge_stage_size;
      struct idetape_bh *bh;
      char *b_data;
      int b_count;
      
      /*
       *    Pipeline parameters.
       *
       *    To accomplish non-pipelined mode, we simply set the following
       *    variables to zero (or NULL, where appropriate).
       */
      /* Number of currently used stages */
      int nr_stages;
      /* Number of pending stages */
      int nr_pending_stages;
      /* We will not allocate more than this number of stages */
      int max_stages, min_pipeline, max_pipeline;
      /* The first stage which will be removed from the pipeline */
      idetape_stage_t *first_stage;
      /* The currently active stage */
      idetape_stage_t *active_stage;
      /* Will be serviced after the currently active request */
      idetape_stage_t *next_stage;
      /* New requests will be added to the pipeline here */
      idetape_stage_t *last_stage;
      /* Optional free stage which we can use */
      idetape_stage_t *cache_stage;
      int pages_per_stage;
      /* Wasted space in each stage */
      int excess_bh_size;

      /* Status/Action flags: long for set_bit */
      unsigned long flags;
      /* protects the ide-tape queue */
      spinlock_t spinlock;

      /*
       * Measures average tape speed
       */
      unsigned long avg_time;
      int avg_size;
      int avg_speed;

      /* last sense information */
      idetape_request_sense_result_t sense;

      char vendor_id[10];
      char product_id[18];
      char firmware_revision[6];
      int firmware_revision_num;

      /* the door is currently locked */
      int door_locked;
      /* the tape hardware is write protected */
      char drv_write_prot;
      /* the tape is write protected (hardware or opened as read-only) */
      char write_prot;

      /*
       * Limit the number of times a request can
       * be postponed, to avoid an infinite postpone
       * deadlock.
       */
      /* request postpone count limit */
      int postpone_cnt;

      /*
       * Measures number of frames:
       *
       * 1. written/read to/from the driver pipeline (pipeline_head).
       * 2. written/read to/from the tape buffers (idetape_bh).
       * 3. written/read by the tape to/from the media (tape_head).
       */
      int pipeline_head;
      int buffer_head;
      int tape_head;
      int last_tape_head;

      /*
       * Speed control at the tape buffers input/output
       */
      unsigned long insert_time;
      int insert_size;
      int insert_speed;
      int max_insert_speed;
      int measure_insert_time;

      /*
       * Measure tape still time, in milliseconds
       */
      unsigned long tape_still_time_begin;
      int tape_still_time;

      /*
       * Speed regulation negative feedback loop
       */
      int speed_control;
      int pipeline_head_speed;
      int controlled_pipeline_head_speed;
      int uncontrolled_pipeline_head_speed;
      int controlled_last_pipeline_head;
      int uncontrolled_last_pipeline_head;
      unsigned long uncontrolled_pipeline_head_time;
      unsigned long controlled_pipeline_head_time;
      int controlled_previous_pipeline_head;
      int uncontrolled_previous_pipeline_head;
      unsigned long controlled_previous_head_time;
      unsigned long uncontrolled_previous_head_time;
      int restart_speed_control_req;

        /*
         * Debug_level determines amount of debugging output;
         * can be changed using /proc/ide/hdx/settings
         * 0 : almost no debugging output
         * 1 : 0+output errors only
         * 2 : 1+output all sensekey/asc
         * 3 : 2+follow all chrdev related procedures
         * 4 : 3+follow all procedures
         * 5 : 4+include pc_stack rq_stack info
         * 6 : 5+USE_COUNT updates
         */
         int debug_level; 
} idetape_tape_t;

static DEFINE_MUTEX(idetape_ref_mutex);

static struct class *idetape_sysfs_class;

#define to_ide_tape(obj) container_of(obj, struct ide_tape_obj, kref)

#define ide_tape_g(disk) \
      container_of((disk)->private_data, struct ide_tape_obj, driver)

static struct ide_tape_obj *ide_tape_get(struct gendisk *disk)
{
      struct ide_tape_obj *tape = NULL;

      mutex_lock(&idetape_ref_mutex);
      tape = ide_tape_g(disk);
      if (tape)
            kref_get(&tape->kref);
      mutex_unlock(&idetape_ref_mutex);
      return tape;
}

static void ide_tape_release(struct kref *);

static void ide_tape_put(struct ide_tape_obj *tape)
{
      mutex_lock(&idetape_ref_mutex);
      kref_put(&tape->kref, ide_tape_release);
      mutex_unlock(&idetape_ref_mutex);
}

/*
 *    Tape door status
 */
#define DOOR_UNLOCKED               0
#define DOOR_LOCKED                 1
#define DOOR_EXPLICITLY_LOCKED            2

/*
 *    Tape flag bits values.
 */
#define IDETAPE_IGNORE_DSC          0
#define IDETAPE_ADDRESS_VALID       1     /* 0 When the tape position is unknown */
#define IDETAPE_BUSY                2     /* Device already opened */
#define IDETAPE_PIPELINE_ERROR            3     /* Error detected in a pipeline stage */
#define IDETAPE_DETECT_BS           4     /* Attempt to auto-detect the current user block size */
#define IDETAPE_FILEMARK            5     /* Currently on a filemark */
#define IDETAPE_DRQ_INTERRUPT       6     /* DRQ interrupt device */
#define IDETAPE_READ_ERROR          7
#define IDETAPE_PIPELINE_ACTIVE           8     /* pipeline active */
/* 0 = no tape is loaded, so we don't rewind after ejecting */
#define IDETAPE_MEDIUM_PRESENT            9

/*
 *    Supported ATAPI tape drives packet commands
 */
#define IDETAPE_TEST_UNIT_READY_CMD 0x00
#define IDETAPE_REWIND_CMD          0x01
#define IDETAPE_REQUEST_SENSE_CMD   0x03
#define IDETAPE_READ_CMD            0x08
#define IDETAPE_WRITE_CMD           0x0a
#define IDETAPE_WRITE_FILEMARK_CMD  0x10
#define IDETAPE_SPACE_CMD           0x11
#define IDETAPE_INQUIRY_CMD         0x12
#define IDETAPE_ERASE_CMD           0x19
#define IDETAPE_MODE_SENSE_CMD            0x1a
#define IDETAPE_MODE_SELECT_CMD           0x15
#define IDETAPE_LOAD_UNLOAD_CMD           0x1b
#define IDETAPE_PREVENT_CMD         0x1e
#define IDETAPE_LOCATE_CMD          0x2b
#define IDETAPE_READ_POSITION_CMD   0x34
#define IDETAPE_READ_BUFFER_CMD           0x3c
#define IDETAPE_SET_SPEED_CMD       0xbb

/*
 *    Some defines for the READ BUFFER command
 */
#define IDETAPE_RETRIEVE_FAULTY_BLOCK     6

/*
 *    Some defines for the SPACE command
 */
#define IDETAPE_SPACE_OVER_FILEMARK 1
#define IDETAPE_SPACE_TO_EOD        3

/*
 *    Some defines for the LOAD UNLOAD command
 */
#define IDETAPE_LU_LOAD_MASK        1
#define IDETAPE_LU_RETENSION_MASK   2
#define IDETAPE_LU_EOT_MASK         4

/*
 *    Special requests for our block device strategy routine.
 *
 *    In order to service a character device command, we add special
 *    requests to the tail of our block device request queue and wait
 *    for their completion.
 */

enum {
      REQ_IDETAPE_PC1         = (1 << 0), /* packet command (first stage) */
      REQ_IDETAPE_PC2         = (1 << 1), /* packet command (second stage) */
      REQ_IDETAPE_READ  = (1 << 2),
      REQ_IDETAPE_WRITE = (1 << 3),
      REQ_IDETAPE_READ_BUFFER = (1 << 4),
};

/*
 *    Error codes which are returned in rq->errors to the higher part
 *    of the driver.
 */
#define     IDETAPE_ERROR_GENERAL         101
#define     IDETAPE_ERROR_FILEMARK        102
#define     IDETAPE_ERROR_EOD       103

/*
 *    The following is used to format the general configuration word of
 *    the ATAPI IDENTIFY DEVICE command.
 */
struct idetape_id_gcw { 
      unsigned packet_size          :2;   /* Packet Size */
      unsigned reserved234          :3;   /* Reserved */
      unsigned drq_type       :2;   /* Command packet DRQ type */
      unsigned removable            :1;   /* Removable media */
      unsigned device_type          :5;   /* Device type */
      unsigned reserved13           :1;   /* Reserved */
      unsigned protocol       :2;   /* Protocol type */
};

/*
 *    INQUIRY packet command - Data Format (From Table 6-8 of QIC-157C)
 */
typedef struct {
      unsigned    device_type :5;   /* Peripheral Device Type */
      unsigned    reserved0_765     :3;   /* Peripheral Qualifier - Reserved */
      unsigned    reserved1_6t0     :7;   /* Reserved */
      unsigned    rmb         :1;   /* Removable Medium Bit */
      unsigned    ansi_version      :3;   /* ANSI Version */
      unsigned    ecma_version      :3;   /* ECMA Version */
      unsigned    iso_version :2;   /* ISO Version */
      unsigned    response_format :4;     /* Response Data Format */
      unsigned    reserved3_45      :2;   /* Reserved */
      unsigned    reserved3_6 :1;   /* TrmIOP - Reserved */
      unsigned    reserved3_7 :1;   /* AENC - Reserved */
      __u8        additional_length;      /* Additional Length (total_length-4) */
      __u8        rsv5, rsv6, rsv7; /* Reserved */
      __u8        vendor_id[8];           /* Vendor Identification */
      __u8        product_id[16];         /* Product Identification */
      __u8        revision_level[4];      /* Revision Level */
      __u8        vendor_specific[20];    /* Vendor Specific - Optional */
      __u8        reserved56t95[40];      /* Reserved - Optional */
                                    /* Additional information may be returned */
} idetape_inquiry_result_t;

/*
 *    READ POSITION packet command - Data Format (From Table 6-57)
 */
typedef struct {
      unsigned    reserved0_10      :2;   /* Reserved */
      unsigned    bpu         :1;   /* Block Position Unknown */  
      unsigned    reserved0_543     :3;   /* Reserved */
      unsigned    eop         :1;   /* End Of Partition */
      unsigned    bop         :1;   /* Beginning Of Partition */
      u8          partition;        /* Partition Number */
      u8          reserved2, reserved3;   /* Reserved */
      u32         first_block;            /* First Block Location */
      u32         last_block;       /* Last Block Location (Optional) */
      u8          reserved12;       /* Reserved */
      u8          blocks_in_buffer[3];    /* Blocks In Buffer - (Optional) */
      u32         bytes_in_buffer;  /* Bytes In Buffer (Optional) */
} idetape_read_position_result_t;

/*
 *    Follows structures which are related to the SELECT SENSE / MODE SENSE
 *    packet commands. Those packet commands are still not supported
 *    by ide-tape.
 */
#define IDETAPE_BLOCK_DESCRIPTOR    0
#define     IDETAPE_CAPABILITIES_PAGE     0x2a
#define IDETAPE_PARAMTR_PAGE        0x2b   /* Onstream DI-x0 only */
#define IDETAPE_BLOCK_SIZE_PAGE           0x30
#define IDETAPE_BUFFER_FILLING_PAGE 0x33

/*
 *    Mode Parameter Header for the MODE SENSE packet command
 */
typedef struct {
      __u8  mode_data_length; /* Length of the following data transfer */
      __u8  medium_type;            /* Medium Type */
      __u8  dsp;              /* Device Specific Parameter */
      __u8  bdl;              /* Block Descriptor Length */
#if 0
      /* data transfer page */
      __u8  page_code   :6;
      __u8  reserved0_6 :1;
      __u8  ps          :1;   /* parameters saveable */
      __u8  page_length;            /* page Length == 0x02 */
      __u8  reserved2;
      __u8  read32k           :1;   /* 32k blk size (data only) */
      __u8  read32k5    :1;   /* 32.5k blk size (data&AUX) */
      __u8  reserved3_23      :2;
      __u8  write32k    :1;   /* 32k blk size (data only) */
      __u8  write32k5   :1;   /* 32.5k blk size (data&AUX) */
      __u8  reserved3_6 :1;
      __u8  streaming   :1;   /* streaming mode enable */
#endif
} idetape_mode_parameter_header_t;

/*
 *    Mode Parameter Block Descriptor the MODE SENSE packet command
 *
 *    Support for block descriptors is optional.
 */
typedef struct {
      __u8        density_code;           /* Medium density code */
      __u8        blocks[3];        /* Number of blocks */
      __u8        reserved4;        /* Reserved */
      __u8        length[3];        /* Block Length */
} idetape_parameter_block_descriptor_t;

/*
 *    The Data Compression Page, as returned by the MODE SENSE packet command.
 */
typedef struct {
      unsigned    page_code   :6;   /* Page Code - Should be 0xf */
      unsigned    reserved0   :1;   /* Reserved */
      unsigned    ps          :1;
      __u8        page_length;            /* Page Length - Should be 14 */
      unsigned    reserved2   :6;   /* Reserved */
      unsigned    dcc         :1;   /* Data Compression Capable */
      unsigned    dce         :1;   /* Data Compression Enable */
      unsigned    reserved3   :5;   /* Reserved */
      unsigned    red         :2;   /* Report Exception on Decompression */
      unsigned    dde         :1;   /* Data Decompression Enable */
      __u32       ca;               /* Compression Algorithm */
      __u32       da;               /* Decompression Algorithm */
      __u8        reserved[4];            /* Reserved */
} idetape_data_compression_page_t;

/*
 *    The Medium Partition Page, as returned by the MODE SENSE packet command.
 */
typedef struct {
      unsigned    page_code   :6;   /* Page Code - Should be 0x11 */
      unsigned    reserved1_6 :1;   /* Reserved */
      unsigned    ps          :1;
      __u8        page_length;            /* Page Length - Should be 6 */
      __u8        map;              /* Maximum Additional Partitions - Should be 0 */
      __u8        apd;              /* Additional Partitions Defined - Should be 0 */
      unsigned    reserved4_012     :3;   /* Reserved */
      unsigned    psum        :2;   /* Should be 0 */
      unsigned    idp         :1;   /* Should be 0 */
      unsigned    sdp         :1;   /* Should be 0 */
      unsigned    fdp         :1;   /* Fixed Data Partitions */
      __u8        mfr;              /* Medium Format Recognition */
      __u8        reserved[2];            /* Reserved */
} idetape_medium_partition_page_t;

/*
 *    Run time configurable parameters.
 */
typedef struct {
      int   dsc_rw_frequency;
      int   dsc_media_access_frequency;
      int   nr_stages;
} idetape_config_t;

/*
 *    The variables below are used for the character device interface.
 *    Additional state variables are defined in our ide_drive_t structure.
 */
static struct ide_tape_obj * idetape_devs[MAX_HWIFS * MAX_DRIVES];

#define ide_tape_f(file) ((file)->private_data)

static struct ide_tape_obj *ide_tape_chrdev_get(unsigned int i)
{
      struct ide_tape_obj *tape = NULL;

      mutex_lock(&idetape_ref_mutex);
      tape = idetape_devs[i];
      if (tape)
            kref_get(&tape->kref);
      mutex_unlock(&idetape_ref_mutex);
      return tape;
}

/*
 *      Function declarations
 *
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp);
static void idetape_write_release (ide_drive_t *drive, unsigned int minor);

/*
 * Too bad. The drive wants to send us data which we are not ready to accept.
 * Just throw it away.
 */
static void idetape_discard_data (ide_drive_t *drive, unsigned int bcount)
{
      while (bcount--)
            (void) HWIF(drive)->INB(IDE_DATA_REG);
}

static void idetape_input_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
      struct idetape_bh *bh = pc->bh;
      int count;

      while (bcount) {
#if IDETAPE_DEBUG_BUGS
            if (bh == NULL) {
                  printk(KERN_ERR "ide-tape: bh == NULL in "
                        "idetape_input_buffers\n");
                  idetape_discard_data(drive, bcount);
                  return;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), bcount);
            HWIF(drive)->atapi_input_bytes(drive, bh->b_data + atomic_read(&bh->b_count), count);
            bcount -= count;
            atomic_add(count, &bh->b_count);
            if (atomic_read(&bh->b_count) == bh->b_size) {
                  bh = bh->b_reqnext;
                  if (bh)
                        atomic_set(&bh->b_count, 0);
            }
      }
      pc->bh = bh;
}

static void idetape_output_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
      struct idetape_bh *bh = pc->bh;
      int count;

      while (bcount) {
#if IDETAPE_DEBUG_BUGS
            if (bh == NULL) {
                  printk(KERN_ERR "ide-tape: bh == NULL in "
                        "idetape_output_buffers\n");
                  return;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            count = min((unsigned int)pc->b_count, (unsigned int)bcount);
            HWIF(drive)->atapi_output_bytes(drive, pc->b_data, count);
            bcount -= count;
            pc->b_data += count;
            pc->b_count -= count;
            if (!pc->b_count) {
                  pc->bh = bh = bh->b_reqnext;
                  if (bh) {
                        pc->b_data = bh->b_data;
                        pc->b_count = atomic_read(&bh->b_count);
                  }
            }
      }
}

static void idetape_update_buffers (idetape_pc_t *pc)
{
      struct idetape_bh *bh = pc->bh;
      int count;
      unsigned int bcount = pc->actually_transferred;

      if (test_bit(PC_WRITING, &pc->flags))
            return;
      while (bcount) {
#if IDETAPE_DEBUG_BUGS
            if (bh == NULL) {
                  printk(KERN_ERR "ide-tape: bh == NULL in "
                        "idetape_update_buffers\n");
                  return;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            count = min((unsigned int)bh->b_size, (unsigned int)bcount);
            atomic_set(&bh->b_count, count);
            if (atomic_read(&bh->b_count) == bh->b_size)
                  bh = bh->b_reqnext;
            bcount -= count;
      }
      pc->bh = bh;
}

/*
 *    idetape_next_pc_storage returns a pointer to a place in which we can
 *    safely store a packet command, even though we intend to leave the
 *    driver. A storage space for a maximum of IDETAPE_PC_STACK packet
 *    commands is allocated at initialization time.
 */
static idetape_pc_t *idetape_next_pc_storage (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 5)
            printk(KERN_INFO "ide-tape: pc_stack_index=%d\n",
                  tape->pc_stack_index);
#endif /* IDETAPE_DEBUG_LOG */
      if (tape->pc_stack_index == IDETAPE_PC_STACK)
            tape->pc_stack_index=0;
      return (&tape->pc_stack[tape->pc_stack_index++]);
}

/*
 *    idetape_next_rq_storage is used along with idetape_next_pc_storage.
 *    Since we queue packet commands in the request queue, we need to
 *    allocate a request, along with the allocation of a packet command.
 */
 
/**************************************************************
 *                                                            *
 *  This should get fixed to use kmalloc(.., GFP_ATOMIC)      *
 *  followed later on by kfree().   -ml                       *
 *                                                            *
 **************************************************************/
 
static struct request *idetape_next_rq_storage (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 5)
            printk(KERN_INFO "ide-tape: rq_stack_index=%d\n",
                  tape->rq_stack_index);
#endif /* IDETAPE_DEBUG_LOG */
      if (tape->rq_stack_index == IDETAPE_PC_STACK)
            tape->rq_stack_index=0;
      return (&tape->rq_stack[tape->rq_stack_index++]);
}

/*
 *    idetape_init_pc initializes a packet command.
 */
static void idetape_init_pc (idetape_pc_t *pc)
{
      memset(pc->c, 0, 12);
      pc->retries = 0;
      pc->flags = 0;
      pc->request_transfer = 0;
      pc->buffer = pc->pc_buffer;
      pc->buffer_size = IDETAPE_PC_BUFFER_SIZE;
      pc->bh = NULL;
      pc->b_data = NULL;
}

/*
 *    idetape_analyze_error is called on each failed packet command retry
 *    to analyze the request sense. We currently do not utilize this
 *    information.
 */
static void idetape_analyze_error (ide_drive_t *drive, idetape_request_sense_result_t *result)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t *pc = tape->failed_pc;

      tape->sense     = *result;
      tape->sense_key = result->sense_key;
      tape->asc       = result->asc;
      tape->ascq      = result->ascq;
#if IDETAPE_DEBUG_LOG
      /*
       *    Without debugging, we only log an error if we decided to
       *    give up retrying.
       */
      if (tape->debug_level >= 1)
            printk(KERN_INFO "ide-tape: pc = %x, sense key = %x, "
                  "asc = %x, ascq = %x\n",
                  pc->c[0], result->sense_key,
                  result->asc, result->ascq);
#endif /* IDETAPE_DEBUG_LOG */

      /*
       *    Correct pc->actually_transferred by asking the tape.
       */
      if (test_bit(PC_DMA_ERROR, &pc->flags)) {
            pc->actually_transferred = pc->request_transfer - tape->tape_block_size * ntohl(get_unaligned(&result->information));
            idetape_update_buffers(pc);
      }

      /*
       * If error was the result of a zero-length read or write command,
       * with sense key=5, asc=0x22, ascq=0, let it slide.  Some drives
       * (i.e. Seagate STT3401A Travan) don't support 0-length read/writes.
       */
      if ((pc->c[0] == IDETAPE_READ_CMD || pc->c[0] == IDETAPE_WRITE_CMD)
          && pc->c[4] == 0 && pc->c[3] == 0 && pc->c[2] == 0) { /* length==0 */
            if (result->sense_key == 5) {
                  /* don't report an error, everything's ok */
                  pc->error = 0;
                  /* don't retry read/write */
                  set_bit(PC_ABORT, &pc->flags);
            }
      }
      if (pc->c[0] == IDETAPE_READ_CMD && result->filemark) {
            pc->error = IDETAPE_ERROR_FILEMARK;
            set_bit(PC_ABORT, &pc->flags);
      }
      if (pc->c[0] == IDETAPE_WRITE_CMD) {
            if (result->eom ||
                (result->sense_key == 0xd && result->asc == 0x0 &&
                 result->ascq == 0x2)) {
                  pc->error = IDETAPE_ERROR_EOD;
                  set_bit(PC_ABORT, &pc->flags);
            }
      }
      if (pc->c[0] == IDETAPE_READ_CMD || pc->c[0] == IDETAPE_WRITE_CMD) {
            if (result->sense_key == 8) {
                  pc->error = IDETAPE_ERROR_EOD;
                  set_bit(PC_ABORT, &pc->flags);
            }
            if (!test_bit(PC_ABORT, &pc->flags) &&
                pc->actually_transferred)
                  pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
      }
}

/*
 * idetape_active_next_stage will declare the next stage as "active".
 */
static void idetape_active_next_stage (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *stage = tape->next_stage;
      struct request *rq = &stage->rq;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_active_next_stage\n");
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
      if (stage == NULL) {
            printk(KERN_ERR "ide-tape: bug: Trying to activate a non existing stage\n");
            return;
      }
#endif /* IDETAPE_DEBUG_BUGS */     

      rq->rq_disk = tape->disk;
      rq->buffer = NULL;
      rq->special = (void *)stage->bh;
      tape->active_data_request = rq;
      tape->active_stage = stage;
      tape->next_stage = stage->next;
}

/*
 *    idetape_increase_max_pipeline_stages is a part of the feedback
 *    loop which tries to find the optimum number of stages. In the
 *    feedback loop, we are starting from a minimum maximum number of
 *    stages, and if we sense that the pipeline is empty, we try to
 *    increase it, until we reach the user compile time memory limit.
 */
static void idetape_increase_max_pipeline_stages (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      int increase = (tape->max_pipeline - tape->min_pipeline) / 10;
      
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk (KERN_INFO "ide-tape: Reached idetape_increase_max_pipeline_stages\n");
#endif /* IDETAPE_DEBUG_LOG */

      tape->max_stages += max(increase, 1);
      tape->max_stages = max(tape->max_stages, tape->min_pipeline);
      tape->max_stages = min(tape->max_stages, tape->max_pipeline);
}

/*
 *    idetape_kfree_stage calls kfree to completely free a stage, along with
 *    its related buffers.
 */
static void __idetape_kfree_stage (idetape_stage_t *stage)
{
      struct idetape_bh *prev_bh, *bh = stage->bh;
      int size;

      while (bh != NULL) {
            if (bh->b_data != NULL) {
                  size = (int) bh->b_size;
                  while (size > 0) {
                        free_page((unsigned long) bh->b_data);
                        size -= PAGE_SIZE;
                        bh->b_data += PAGE_SIZE;
                  }
            }
            prev_bh = bh;
            bh = bh->b_reqnext;
            kfree(prev_bh);
      }
      kfree(stage);
}

static void idetape_kfree_stage (idetape_tape_t *tape, idetape_stage_t *stage)
{
      __idetape_kfree_stage(stage);
}

/*
 *    idetape_remove_stage_head removes tape->first_stage from the pipeline.
 *    The caller should avoid race conditions.
 */
static void idetape_remove_stage_head (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *stage;
      
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_remove_stage_head\n");
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
      if (tape->first_stage == NULL) {
            printk(KERN_ERR "ide-tape: bug: tape->first_stage is NULL\n");
            return;           
      }
      if (tape->active_stage == tape->first_stage) {
            printk(KERN_ERR "ide-tape: bug: Trying to free our active pipeline stage\n");
            return;
      }
#endif /* IDETAPE_DEBUG_BUGS */
      stage = tape->first_stage;
      tape->first_stage = stage->next;
      idetape_kfree_stage(tape, stage);
      tape->nr_stages--;
      if (tape->first_stage == NULL) {
            tape->last_stage = NULL;
#if IDETAPE_DEBUG_BUGS
            if (tape->next_stage != NULL)
                  printk(KERN_ERR "ide-tape: bug: tape->next_stage != NULL\n");
            if (tape->nr_stages)
                  printk(KERN_ERR "ide-tape: bug: nr_stages should be 0 now\n");
#endif /* IDETAPE_DEBUG_BUGS */
      }
}

/*
 * This will free all the pipeline stages starting from new_last_stage->next
 * to the end of the list, and point tape->last_stage to new_last_stage.
 */
static void idetape_abort_pipeline(ide_drive_t *drive,
                           idetape_stage_t *new_last_stage)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *stage = new_last_stage->next;
      idetape_stage_t *nstage;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: %s: idetape_abort_pipeline called\n", tape->name);
#endif
      while (stage) {
            nstage = stage->next;
            idetape_kfree_stage(tape, stage);
            --tape->nr_stages;
            --tape->nr_pending_stages;
            stage = nstage;
      }
      if (new_last_stage)
            new_last_stage->next = NULL;
      tape->last_stage = new_last_stage;
      tape->next_stage = NULL;
}

/*
 *    idetape_end_request is used to finish servicing a request, and to
 *    insert a pending pipeline request into the main device queue.
 */
static int idetape_end_request(ide_drive_t *drive, int uptodate, int nr_sects)
{
      struct request *rq = HWGROUP(drive)->rq;
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;
      int error;
      int remove_stage = 0;
      idetape_stage_t *active_stage;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
      printk(KERN_INFO "ide-tape: Reached idetape_end_request\n");
#endif /* IDETAPE_DEBUG_LOG */

      switch (uptodate) {
            case 0:     error = IDETAPE_ERROR_GENERAL; break;
            case 1: error = 0; break;
            default: error = uptodate;
      }
      rq->errors = error;
      if (error)
            tape->failed_pc = NULL;

      spin_lock_irqsave(&tape->spinlock, flags);

      /* The request was a pipelined data transfer request */
      if (tape->active_data_request == rq) {
            active_stage = tape->active_stage;
            tape->active_stage = NULL;
            tape->active_data_request = NULL;
            tape->nr_pending_stages--;
            if (rq->cmd[0] & REQ_IDETAPE_WRITE) {
                  remove_stage = 1;
                  if (error) {
                        set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
                        if (error == IDETAPE_ERROR_EOD)
                              idetape_abort_pipeline(drive, active_stage);
                  }
            } else if (rq->cmd[0] & REQ_IDETAPE_READ) {
                  if (error == IDETAPE_ERROR_EOD) {
                        set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
                        idetape_abort_pipeline(drive, active_stage);
                  }
            }
            if (tape->next_stage != NULL) {
                  idetape_active_next_stage(drive);

                  /*
                   * Insert the next request into the request queue.
                   */
                  (void) ide_do_drive_cmd(drive, tape->active_data_request, ide_end);
            } else if (!error) {
                        idetape_increase_max_pipeline_stages(drive);
            }
      }
      ide_end_drive_cmd(drive, 0, 0);
//    blkdev_dequeue_request(rq);
//    drive->rq = NULL;
//    end_that_request_last(rq);

      if (remove_stage)
            idetape_remove_stage_head(drive);
      if (tape->active_data_request == NULL)
            clear_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
      spin_unlock_irqrestore(&tape->spinlock, flags);
      return 0;
}

static ide_startstop_t idetape_request_sense_callback (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_request_sense_callback\n");
#endif /* IDETAPE_DEBUG_LOG */
      if (!tape->pc->error) {
            idetape_analyze_error(drive, (idetape_request_sense_result_t *) tape->pc->buffer);
            idetape_end_request(drive, 1, 0);
      } else {
            printk(KERN_ERR "ide-tape: Error in REQUEST SENSE itself - Aborting request!\n");
            idetape_end_request(drive, 0, 0);
      }
      return ide_stopped;
}

static void idetape_create_request_sense_cmd (idetape_pc_t *pc)
{
      idetape_init_pc(pc);    
      pc->c[0] = IDETAPE_REQUEST_SENSE_CMD;
      pc->c[4] = 20;
      pc->request_transfer = 20;
      pc->callback = &idetape_request_sense_callback;
}

static void idetape_init_rq(struct request *rq, u8 cmd)
{
      memset(rq, 0, sizeof(*rq));
      rq->flags = REQ_SPECIAL;
      rq->cmd[0] = cmd;
}

/*
 *    idetape_queue_pc_head generates a new packet command request in front
 *    of the request queue, before the current request, so that it will be
 *    processed immediately, on the next pass through the driver.
 *
 *    idetape_queue_pc_head is called from the request handling part of
 *    the driver (the "bottom" part). Safe storage for the request should
 *    be allocated with idetape_next_pc_storage and idetape_next_rq_storage
 *    before calling idetape_queue_pc_head.
 *
 *    Memory for those requests is pre-allocated at initialization time, and
 *    is limited to IDETAPE_PC_STACK requests. We assume that we have enough
 *    space for the maximum possible number of inter-dependent packet commands.
 *
 *    The higher level of the driver - The ioctl handler and the character
 *    device handling functions should queue request to the lower level part
 *    and wait for their completion using idetape_queue_pc_tail or
 *    idetape_queue_rw_tail.
 */
static void idetape_queue_pc_head (ide_drive_t *drive, idetape_pc_t *pc,struct request *rq)
{
      struct ide_tape_obj *tape = drive->driver_data;

      idetape_init_rq(rq, REQ_IDETAPE_PC1);
      rq->buffer = (char *) pc;
      rq->rq_disk = tape->disk;
      (void) ide_do_drive_cmd(drive, rq, ide_preempt);
}

/*
 *    idetape_retry_pc is called when an error was detected during the
 *    last packet command. We queue a request sense packet command in
 *    the head of the request list.
 */
static ide_startstop_t idetape_retry_pc (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t *pc;
      struct request *rq;
      atapi_error_t error;

      error.all = HWIF(drive)->INB(IDE_ERROR_REG);
      pc = idetape_next_pc_storage(drive);
      rq = idetape_next_rq_storage(drive);
      idetape_create_request_sense_cmd(pc);
      set_bit(IDETAPE_IGNORE_DSC, &tape->flags);
      idetape_queue_pc_head(drive, pc, rq);
      return ide_stopped;
}

/*
 *    idetape_postpone_request postpones the current request so that
 *    ide.c will be able to service requests from another device on
 *    the same hwgroup while we are polling for DSC.
 */
static void idetape_postpone_request (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: idetape_postpone_request\n");
#endif
      tape->postponed_rq = HWGROUP(drive)->rq;
      ide_stall_queue(drive, tape->dsc_polling_frequency);
}

/*
 *    idetape_pc_intr is the usual interrupt handler which will be called
 *    during a packet command. We will transfer some of the data (as
 *    requested by the drive) and will re-point interrupt handler to us.
 *    When data transfer is finished, we will act according to the
 *    algorithm described before idetape_issue_packet_command.
 *
 */
static ide_startstop_t idetape_pc_intr (ide_drive_t *drive)
{
      ide_hwif_t *hwif = drive->hwif;
      idetape_tape_t *tape = drive->driver_data;
      atapi_status_t status;
      atapi_bcount_t bcount;
      atapi_ireason_t ireason;
      idetape_pc_t *pc = tape->pc;

      unsigned int temp;
#if SIMULATE_ERRORS
      static int error_sim_count = 0;
#endif

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_pc_intr "
                        "interrupt handler\n");
#endif /* IDETAPE_DEBUG_LOG */      

      /* Clear the interrupt */
      status.all = HWIF(drive)->INB(IDE_STATUS_REG);

      if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
            if (HWIF(drive)->ide_dma_end(drive) || status.b.check) {
                  /*
                   * A DMA error is sometimes expected. For example,
                   * if the tape is crossing a filemark during a
                   * READ command, it will issue an irq and position
                   * itself before the filemark, so that only a partial
                   * data transfer will occur (which causes the DMA
                   * error). In that case, we will later ask the tape
                   * how much bytes of the original request were
                   * actually transferred (we can't receive that
                   * information from the DMA engine on most chipsets).
                   */

                  /*
                   * On the contrary, a DMA error is never expected;
                   * it usually indicates a hardware error or abort.
                   * If the tape crosses a filemark during a READ
                   * command, it will issue an irq and position itself
                   * after the filemark (not before). Only a partial
                   * data transfer will occur, but no DMA error.
                   * (AS, 19 Apr 2001)
                   */
                  set_bit(PC_DMA_ERROR, &pc->flags);
            } else {
                  pc->actually_transferred = pc->request_transfer;
                  idetape_update_buffers(pc);
            }
#if IDETAPE_DEBUG_LOG
            if (tape->debug_level >= 4)
                  printk(KERN_INFO "ide-tape: DMA finished\n");
#endif /* IDETAPE_DEBUG_LOG */
      }

      /* No more interrupts */
      if (!status.b.drq) {
#if IDETAPE_DEBUG_LOG
            if (tape->debug_level >= 2)
                  printk(KERN_INFO "ide-tape: Packet command completed, %d bytes transferred\n", pc->actually_transferred);
#endif /* IDETAPE_DEBUG_LOG */
            clear_bit(PC_DMA_IN_PROGRESS, &pc->flags);

            local_irq_enable();

#if SIMULATE_ERRORS
            if ((pc->c[0] == IDETAPE_WRITE_CMD ||
                 pc->c[0] == IDETAPE_READ_CMD) &&
                (++error_sim_count % 100) == 0) {
                  printk(KERN_INFO "ide-tape: %s: simulating error\n",
                        tape->name);
                  status.b.check = 1;
            }
#endif
            if (status.b.check && pc->c[0] == IDETAPE_REQUEST_SENSE_CMD)
                  status.b.check = 0;
            if (status.b.check || test_bit(PC_DMA_ERROR, &pc->flags)) { /* Error detected */
#if IDETAPE_DEBUG_LOG
                  if (tape->debug_level >= 1)
                        printk(KERN_INFO "ide-tape: %s: I/O error\n",
                              tape->name);
#endif /* IDETAPE_DEBUG_LOG */
                  if (pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
                        printk(KERN_ERR "ide-tape: I/O error in request sense command\n");
                        return ide_do_reset(drive);
                  }
#if IDETAPE_DEBUG_LOG
                  if (tape->debug_level >= 1)
                        printk(KERN_INFO "ide-tape: [cmd %x]: check condition\n", pc->c[0]);
#endif
                  /* Retry operation */
                  return idetape_retry_pc(drive);
            }
            pc->error = 0;
            if (test_bit(PC_WAIT_FOR_DSC, &pc->flags) &&
                !status.b.dsc) {
                  /* Media access command */
                  tape->dsc_polling_start = jiffies;
                  tape->dsc_polling_frequency = IDETAPE_DSC_MA_FAST;
                  tape->dsc_timeout = jiffies + IDETAPE_DSC_MA_TIMEOUT;
                  /* Allow ide.c to handle other requests */
                  idetape_postpone_request(drive);
                  return ide_stopped;
            }
            if (tape->failed_pc == pc)
                  tape->failed_pc = NULL;
            /* Command finished - Call the callback function */
            return pc->callback(drive);
      }
      if (test_and_clear_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
            printk(KERN_ERR "ide-tape: The tape wants to issue more "
                        "interrupts in DMA mode\n");
            printk(KERN_ERR "ide-tape: DMA disabled, reverting to PIO\n");
            (void)__ide_dma_off(drive);
            return ide_do_reset(drive);
      }
      /* Get the number of bytes to transfer on this interrupt. */
      bcount.b.high = hwif->INB(IDE_BCOUNTH_REG);
      bcount.b.low = hwif->INB(IDE_BCOUNTL_REG);

      ireason.all = hwif->INB(IDE_IREASON_REG);

      if (ireason.b.cod) {
            printk(KERN_ERR "ide-tape: CoD != 0 in idetape_pc_intr\n");
            return ide_do_reset(drive);
      }
      if (ireason.b.io == test_bit(PC_WRITING, &pc->flags)) {
            /* Hopefully, we will never get here */
            printk(KERN_ERR "ide-tape: We wanted to %s, ",
                  ireason.b.io ? "Write":"Read");
            printk(KERN_ERR "ide-tape: but the tape wants us to %s !\n",
                  ireason.b.io ? "Read":"Write");
            return ide_do_reset(drive);
      }
      if (!test_bit(PC_WRITING, &pc->flags)) {
            /* Reading - Check that we have enough space */
            temp = pc->actually_transferred + bcount.all;
            if (temp > pc->request_transfer) {
                  if (temp > pc->buffer_size) {
                        printk(KERN_ERR "ide-tape: The tape wants to send us more data than expected - discarding data\n");
                        idetape_discard_data(drive, bcount.all);
                        ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
                        return ide_started;
                  }
#if IDETAPE_DEBUG_LOG
                  if (tape->debug_level >= 2)
                        printk(KERN_NOTICE "ide-tape: The tape wants to send us more data than expected - allowing transfer\n");
#endif /* IDETAPE_DEBUG_LOG */
            }
      }
      if (test_bit(PC_WRITING, &pc->flags)) {
            if (pc->bh != NULL)
                  idetape_output_buffers(drive, pc, bcount.all);
            else
                  /* Write the current buffer */
                  HWIF(drive)->atapi_output_bytes(drive, pc->current_position, bcount.all);
      } else {
            if (pc->bh != NULL)
                  idetape_input_buffers(drive, pc, bcount.all);
            else
                  /* Read the current buffer */
                  HWIF(drive)->atapi_input_bytes(drive, pc->current_position, bcount.all);
      }
      /* Update the current position */
      pc->actually_transferred += bcount.all;
      pc->current_position += bcount.all;
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 2)
            printk(KERN_INFO "ide-tape: [cmd %x] transferred %d bytes on that interrupt\n", pc->c[0], bcount.all);
#endif
      /* And set the interrupt handler again */
      ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
      return ide_started;
}

/*
 *    Packet Command Interface
 *
 *    The current Packet Command is available in tape->pc, and will not
 *    change until we finish handling it. Each packet command is associated
 *    with a callback function that will be called when the command is
 *    finished.
 *
 *    The handling will be done in three stages:
 *
 *    1.    idetape_issue_packet_command will send the packet command to the
 *          drive, and will set the interrupt handler to idetape_pc_intr.
 *
 *    2.    On each interrupt, idetape_pc_intr will be called. This step
 *          will be repeated until the device signals us that no more
 *          interrupts will be issued.
 *
 *    3.    ATAPI Tape media access commands have immediate status with a
 *          delayed process. In case of a successful initiation of a
 *          media access packet command, the DSC bit will be set when the
 *          actual execution of the command is finished. 
 *          Since the tape drive will not issue an interrupt, we have to
 *          poll for this event. In this case, we define the request as
 *          "low priority request" by setting rq_status to
 *          IDETAPE_RQ_POSTPONED,   set a timer to poll for DSC and exit
 *          the driver.
 *
 *          ide.c will then give higher priority to requests which
 *          originate from the other device, until will change rq_status
 *          to RQ_ACTIVE.
 *
 *    4.    When the packet command is finished, it will be checked for errors.
 *
 *    5.    In case an error was found, we queue a request sense packet
 *          command in front of the request queue and retry the operation
 *          up to IDETAPE_MAX_PC_RETRIES times.
 *
 *    6.    In case no error was found, or we decided to give up and not
 *          to retry again, the callback function will be called and then
 *          we will handle the next request.
 *
 */
static ide_startstop_t idetape_transfer_pc(ide_drive_t *drive)
{
      ide_hwif_t *hwif = drive->hwif;
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t *pc = tape->pc;
      atapi_ireason_t ireason;
      int retries = 100;
      ide_startstop_t startstop;

      if (ide_wait_stat(&startstop,drive,DRQ_STAT,BUSY_STAT,WAIT_READY)) {
            printk(KERN_ERR "ide-tape: Strange, packet command initiated yet DRQ isn't asserted\n");
            return startstop;
      }
      ireason.all = hwif->INB(IDE_IREASON_REG);
      while (retries-- && (!ireason.b.cod || ireason.b.io)) {
            printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while issuing "
                        "a packet command, retrying\n");
            udelay(100);
            ireason.all = hwif->INB(IDE_IREASON_REG);
            if (retries == 0) {
                  printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while "
                              "issuing a packet command, ignoring\n");
                  ireason.b.cod = 1;
                  ireason.b.io = 0;
            }
      }
      if (!ireason.b.cod || ireason.b.io) {
            printk(KERN_ERR "ide-tape: (IO,CoD) != (0,1) while issuing "
                        "a packet command\n");
            return ide_do_reset(drive);
      }
      /* Set the interrupt routine */
      ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
#ifdef CONFIG_BLK_DEV_IDEDMA
      /* Begin DMA, if necessary */
      if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags))
            hwif->dma_start(drive);
#endif
      /* Send the actual packet */
      HWIF(drive)->atapi_output_bytes(drive, pc->c, 12);
      return ide_started;
}

static ide_startstop_t idetape_issue_packet_command (ide_drive_t *drive, idetape_pc_t *pc)
{
      ide_hwif_t *hwif = drive->hwif;
      idetape_tape_t *tape = drive->driver_data;
      atapi_bcount_t bcount;
      int dma_ok = 0;

#if IDETAPE_DEBUG_BUGS
      if (tape->pc->c[0] == IDETAPE_REQUEST_SENSE_CMD &&
          pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
            printk(KERN_ERR "ide-tape: possible ide-tape.c bug - "
                  "Two request sense in serial were issued\n");
      }
#endif /* IDETAPE_DEBUG_BUGS */

      if (tape->failed_pc == NULL && pc->c[0] != IDETAPE_REQUEST_SENSE_CMD)
            tape->failed_pc = pc;
      /* Set the current packet command */
      tape->pc = pc;

      if (pc->retries > IDETAPE_MAX_PC_RETRIES ||
          test_bit(PC_ABORT, &pc->flags)) {
            /*
             *    We will "abort" retrying a packet command in case
             *    a legitimate error code was received (crossing a
             *    filemark, or end of the media, for example).
             */
            if (!test_bit(PC_ABORT, &pc->flags)) {
                  if (!(pc->c[0] == IDETAPE_TEST_UNIT_READY_CMD &&
                        tape->sense_key == 2 && tape->asc == 4 &&
                       (tape->ascq == 1 || tape->ascq == 8))) {
                        printk(KERN_ERR "ide-tape: %s: I/O error, "
                                    "pc = %2x, key = %2x, "
                                    "asc = %2x, ascq = %2x\n",
                                    tape->name, pc->c[0],
                                    tape->sense_key, tape->asc,
                                    tape->ascq);
                  }
                  /* Giving up */
                  pc->error = IDETAPE_ERROR_GENERAL;
            }
            tape->failed_pc = NULL;
            return pc->callback(drive);
      }
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 2)
            printk(KERN_INFO "ide-tape: Retry number - %d, cmd = %02X\n", pc->retries, pc->c[0]);
#endif /* IDETAPE_DEBUG_LOG */

      pc->retries++;
      /* We haven't transferred any data yet */
      pc->actually_transferred = 0;
      pc->current_position = pc->buffer;
      /* Request to transfer the entire buffer at once */
      bcount.all = pc->request_transfer;

      if (test_and_clear_bit(PC_DMA_ERROR, &pc->flags)) {
            printk(KERN_WARNING "ide-tape: DMA disabled, "
                        "reverting to PIO\n");
            (void)__ide_dma_off(drive);
      }
      if (test_bit(PC_DMA_RECOMMENDED, &pc->flags) && drive->using_dma)
            dma_ok = !hwif->dma_setup(drive);

      if (IDE_CONTROL_REG)
            hwif->OUTB(drive->ctl, IDE_CONTROL_REG);
      hwif->OUTB(dma_ok ? 1 : 0, IDE_FEATURE_REG);    /* Use PIO/DMA */
      hwif->OUTB(bcount.b.high, IDE_BCOUNTH_REG);
      hwif->OUTB(bcount.b.low, IDE_BCOUNTL_REG);
      hwif->OUTB(drive->select.all, IDE_SELECT_REG);
      if (dma_ok)             /* Will begin DMA later */
            set_bit(PC_DMA_IN_PROGRESS, &pc->flags);
      if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
            ide_set_handler(drive, &idetape_transfer_pc, IDETAPE_WAIT_CMD, NULL);
            hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
            return ide_started;
      } else {
            hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
            return idetape_transfer_pc(drive);
      }
}

/*
 *    General packet command callback function.
 */
static ide_startstop_t idetape_pc_callback (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_pc_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

      idetape_end_request(drive, tape->pc->error ? 0 : 1, 0);
      return ide_stopped;
}

/*
 *    A mode sense command is used to "sense" tape parameters.
 */
static void idetape_create_mode_sense_cmd (idetape_pc_t *pc, u8 page_code)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_MODE_SENSE_CMD;
      if (page_code != IDETAPE_BLOCK_DESCRIPTOR)
            pc->c[1] = 8;     /* DBD = 1 - Don't return block descriptors */
      pc->c[2] = page_code;
      /*
       * Changed pc->c[3] to 0 (255 will at best return unused info).
       *
       * For SCSI this byte is defined as subpage instead of high byte
       * of length and some IDE drives seem to interpret it this way
       * and return an error when 255 is used.
       */
      pc->c[3] = 0;
      pc->c[4] = 255;         /* (We will just discard data in that case) */
      if (page_code == IDETAPE_BLOCK_DESCRIPTOR)
            pc->request_transfer = 12;
      else if (page_code == IDETAPE_CAPABILITIES_PAGE)
            pc->request_transfer = 24;
      else
            pc->request_transfer = 50;
      pc->callback = &idetape_pc_callback;
}

static void calculate_speeds(ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      int full = 125, empty = 75;

      if (time_after(jiffies, tape->controlled_pipeline_head_time + 120 * HZ)) {
            tape->controlled_previous_pipeline_head = tape->controlled_last_pipeline_head;
            tape->controlled_previous_head_time = tape->controlled_pipeline_head_time;
            tape->controlled_last_pipeline_head = tape->pipeline_head;
            tape->controlled_pipeline_head_time = jiffies;
      }
      if (time_after(jiffies, tape->controlled_pipeline_head_time + 60 * HZ))
            tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_last_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_pipeline_head_time);
      else if (time_after(jiffies, tape->controlled_previous_head_time))
            tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_previous_head_time);

      if (tape->nr_pending_stages < tape->max_stages /*- 1 */) {
            /* -1 for read mode error recovery */
            if (time_after(jiffies, tape->uncontrolled_previous_head_time + 10 * HZ)) {
                  tape->uncontrolled_pipeline_head_time = jiffies;
                  tape->uncontrolled_pipeline_head_speed = (tape->pipeline_head - tape->uncontrolled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->uncontrolled_previous_head_time);
            }
      } else {
            tape->uncontrolled_previous_head_time = jiffies;
            tape->uncontrolled_previous_pipeline_head = tape->pipeline_head;
            if (time_after(jiffies, tape->uncontrolled_pipeline_head_time + 30 * HZ)) {
                  tape->uncontrolled_pipeline_head_time = jiffies;
            }
      }
      tape->pipeline_head_speed = max(tape->uncontrolled_pipeline_head_speed, tape->controlled_pipeline_head_speed);
      if (tape->speed_control == 0) {
            tape->max_insert_speed = 5000;
      } else if (tape->speed_control == 1) {
            if (tape->nr_pending_stages >= tape->max_stages / 2)
                  tape->max_insert_speed = tape->pipeline_head_speed +
                        (1100 - tape->pipeline_head_speed) * 2 * (tape->nr_pending_stages - tape->max_stages / 2) / tape->max_stages;
            else
                  tape->max_insert_speed = 500 +
                        (tape->pipeline_head_speed - 500) * 2 * tape->nr_pending_stages / tape->max_stages;
            if (tape->nr_pending_stages >= tape->max_stages * 99 / 100)
                  tape->max_insert_speed = 5000;
      } else if (tape->speed_control == 2) {
            tape->max_insert_speed = tape->pipeline_head_speed * empty / 100 +
                  (tape->pipeline_head_speed * full / 100 - tape->pipeline_head_speed * empty / 100) * tape->nr_pending_stages / tape->max_stages;
      } else
            tape->max_insert_speed = tape->speed_control;
      tape->max_insert_speed = max(tape->max_insert_speed, 500);
}

static ide_startstop_t idetape_media_access_finished (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t *pc = tape->pc;
      atapi_status_t status;

      status.all = HWIF(drive)->INB(IDE_STATUS_REG);
      if (status.b.dsc) {
            if (status.b.check) {
                  /* Error detected */
                  if (pc->c[0] != IDETAPE_TEST_UNIT_READY_CMD)
                        printk(KERN_ERR "ide-tape: %s: I/O error, ",
                                    tape->name);
                  /* Retry operation */
                  return idetape_retry_pc(drive);
            }
            pc->error = 0;
            if (tape->failed_pc == pc)
                  tape->failed_pc = NULL;
      } else {
            pc->error = IDETAPE_ERROR_GENERAL;
            tape->failed_pc = NULL;
      }
      return pc->callback(drive);
}

static ide_startstop_t idetape_rw_callback (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      struct request *rq = HWGROUP(drive)->rq;
      int blocks = tape->pc->actually_transferred / tape->tape_block_size;

      tape->avg_size += blocks * tape->tape_block_size;
      tape->insert_size += blocks * tape->tape_block_size;
      if (tape->insert_size > 1024 * 1024)
            tape->measure_insert_time = 1;
      if (tape->measure_insert_time) {
            tape->measure_insert_time = 0;
            tape->insert_time = jiffies;
            tape->insert_size = 0;
      }
      if (time_after(jiffies, tape->insert_time))
            tape->insert_speed = tape->insert_size / 1024 * HZ / (jiffies - tape->insert_time);
      if (time_after_eq(jiffies, tape->avg_time + HZ)) {
            tape->avg_speed = tape->avg_size * HZ / (jiffies - tape->avg_time) / 1024;
            tape->avg_size = 0;
            tape->avg_time = jiffies;
      }

#if IDETAPE_DEBUG_LOG   
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_rw_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

      tape->first_frame_position += blocks;
      rq->current_nr_sectors -= blocks;

      if (!tape->pc->error)
            idetape_end_request(drive, 1, 0);
      else
            idetape_end_request(drive, tape->pc->error, 0);
      return ide_stopped;
}

static void idetape_create_read_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_READ_CMD;
      put_unaligned(htonl(length), (unsigned int *) &pc->c[1]);
      pc->c[1] = 1;
      pc->callback = &idetape_rw_callback;
      pc->bh = bh;
      atomic_set(&bh->b_count, 0);
      pc->buffer = NULL;
      pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
      if (pc->request_transfer == tape->stage_size)
            set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

static void idetape_create_read_buffer_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
      int size = 32768;
      struct idetape_bh *p = bh;

      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_READ_BUFFER_CMD;
      pc->c[1] = IDETAPE_RETRIEVE_FAULTY_BLOCK;
      pc->c[7] = size >> 8;
      pc->c[8] = size & 0xff;
      pc->callback = &idetape_pc_callback;
      pc->bh = bh;
      atomic_set(&bh->b_count, 0);
      pc->buffer = NULL;
      while (p) {
            atomic_set(&p->b_count, 0);
            p = p->b_reqnext;
      }
      pc->request_transfer = pc->buffer_size = size;
}

static void idetape_create_write_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_WRITE_CMD;
      put_unaligned(htonl(length), (unsigned int *) &pc->c[1]);
      pc->c[1] = 1;
      pc->callback = &idetape_rw_callback;
      set_bit(PC_WRITING, &pc->flags);
      pc->bh = bh;
      pc->b_data = bh->b_data;
      pc->b_count = atomic_read(&bh->b_count);
      pc->buffer = NULL;
      pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
      if (pc->request_transfer == tape->stage_size)
            set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

/*
 * idetape_do_request is our request handling function.     
 */
static ide_startstop_t idetape_do_request(ide_drive_t *drive,
                                struct request *rq, sector_t block)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t *pc = NULL;
      struct request *postponed_rq = tape->postponed_rq;
      atapi_status_t status;

#if IDETAPE_DEBUG_LOG
#if 0
      if (tape->debug_level >= 5)
            printk(KERN_INFO "ide-tape: rq_status: %d, "
                  "dev: %s, cmd: %ld, errors: %d\n", rq->rq_status,
                   rq->rq_disk->disk_name, rq->cmd[0], rq->errors);
#endif
      if (tape->debug_level >= 2)
            printk(KERN_INFO "ide-tape: sector: %ld, "
                  "nr_sectors: %ld, current_nr_sectors: %d\n",
                  rq->sector, rq->nr_sectors, rq->current_nr_sectors);
#endif /* IDETAPE_DEBUG_LOG */

      if ((rq->flags & REQ_SPECIAL) == 0) {
            /*
             * We do not support buffer cache originated requests.
             */
            printk(KERN_NOTICE "ide-tape: %s: Unsupported request in "
                  "request queue (%ld)\n", drive->name, rq->flags);
            ide_end_request(drive, 0, 0);
            return ide_stopped;
      }

      /*
       *    Retry a failed packet command
       */
      if (tape->failed_pc != NULL &&
          tape->pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
            return idetape_issue_packet_command(drive, tape->failed_pc);
      }
#if IDETAPE_DEBUG_BUGS
      if (postponed_rq != NULL)
            if (rq != postponed_rq) {
                  printk(KERN_ERR "ide-tape: ide-tape.c bug - "
                              "Two DSC requests were queued\n");
                  idetape_end_request(drive, 0, 0);
                  return ide_stopped;
            }
#endif /* IDETAPE_DEBUG_BUGS */

      tape->postponed_rq = NULL;

      /*
       * If the tape is still busy, postpone our request and service
       * the other device meanwhile.
       */
      status.all = HWIF(drive)->INB(IDE_STATUS_REG);

      if (!drive->dsc_overlap && !(rq->cmd[0] & REQ_IDETAPE_PC2))
            set_bit(IDETAPE_IGNORE_DSC, &tape->flags);

      if (drive->post_reset == 1) {
            set_bit(IDETAPE_IGNORE_DSC, &tape->flags);
            drive->post_reset = 0;
      }

      if (tape->tape_still_time > 100 && tape->tape_still_time < 200)
            tape->measure_insert_time = 1;
      if (time_after(jiffies, tape->insert_time))
            tape->insert_speed = tape->insert_size / 1024 * HZ / (jiffies - tape->insert_time);
      calculate_speeds(drive);
      if (!test_and_clear_bit(IDETAPE_IGNORE_DSC, &tape->flags) &&
          !status.b.dsc) {
            if (postponed_rq == NULL) {
                  tape->dsc_polling_start = jiffies;
                  tape->dsc_polling_frequency = tape->best_dsc_rw_frequency;
                  tape->dsc_timeout = jiffies + IDETAPE_DSC_RW_TIMEOUT;
            } else if (time_after(jiffies, tape->dsc_timeout)) {
                  printk(KERN_ERR "ide-tape: %s: DSC timeout\n",
                        tape->name);
                  if (rq->cmd[0] & REQ_IDETAPE_PC2) {
                        idetape_media_access_finished(drive);
                        return ide_stopped;
                  } else {
                        return ide_do_reset(drive);
                  }
            } else if (time_after(jiffies, tape->dsc_polling_start + IDETAPE_DSC_MA_THRESHOLD))
                  tape->dsc_polling_frequency = IDETAPE_DSC_MA_SLOW;
            idetape_postpone_request(drive);
            return ide_stopped;
      }
      if (rq->cmd[0] & REQ_IDETAPE_READ) {
            tape->buffer_head++;
#if USE_IOTRACE
            IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
            tape->postpone_cnt = 0;
            pc = idetape_next_pc_storage(drive);
            idetape_create_read_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
            goto out;
      }
      if (rq->cmd[0] & REQ_IDETAPE_WRITE) {
            tape->buffer_head++;
#if USE_IOTRACE
            IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
            tape->postpone_cnt = 0;
            pc = idetape_next_pc_storage(drive);
            idetape_create_write_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
            goto out;
      }
      if (rq->cmd[0] & REQ_IDETAPE_READ_BUFFER) {
            tape->postpone_cnt = 0;
            pc = idetape_next_pc_storage(drive);
            idetape_create_read_buffer_cmd(tape, pc, rq->current_nr_sectors, (struct idetape_bh *)rq->special);
            goto out;
      }
      if (rq->cmd[0] & REQ_IDETAPE_PC1) {
            pc = (idetape_pc_t *) rq->buffer;
            rq->cmd[0] &= ~(REQ_IDETAPE_PC1);
            rq->cmd[0] |= REQ_IDETAPE_PC2;
            goto out;
      }
      if (rq->cmd[0] & REQ_IDETAPE_PC2) {
            idetape_media_access_finished(drive);
            return ide_stopped;
      }
      BUG();
out:
      return idetape_issue_packet_command(drive, pc);
}

/*
 *    Pipeline related functions
 */
static inline int idetape_pipeline_active (idetape_tape_t *tape)
{
      int rc1, rc2;

      rc1 = test_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
      rc2 = (tape->active_data_request != NULL);
      return rc1;
}

/*
 *    idetape_kmalloc_stage uses __get_free_page to allocate a pipeline
 *    stage, along with all the necessary small buffers which together make
 *    a buffer of size tape->stage_size (or a bit more). We attempt to
 *    combine sequential pages as much as possible.
 *
 *    Returns a pointer to the new allocated stage, or NULL if we
 *    can't (or don't want to) allocate a stage.
 *
 *    Pipeline stages are optional and are used to increase performance.
 *    If we can't allocate them, we'll manage without them.
 */
static idetape_stage_t *__idetape_kmalloc_stage (idetape_tape_t *tape, int full, int clear)
{
      idetape_stage_t *stage;
      struct idetape_bh *prev_bh, *bh;
      int pages = tape->pages_per_stage;
      char *b_data = NULL;

      if ((stage = (idetape_stage_t *) kmalloc (sizeof (idetape_stage_t),GFP_KERNEL)) == NULL)
            return NULL;
      stage->next = NULL;

      bh = stage->bh = (struct idetape_bh *)kmalloc(sizeof(struct idetape_bh), GFP_KERNEL);
      if (bh == NULL)
            goto abort;
      bh->b_reqnext = NULL;
      if ((bh->b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
            goto abort;
      if (clear)
            memset(bh->b_data, 0, PAGE_SIZE);
      bh->b_size = PAGE_SIZE;
      atomic_set(&bh->b_count, full ? bh->b_size : 0);

      while (--pages) {
            if ((b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
                  goto abort;
            if (clear)
                  memset(b_data, 0, PAGE_SIZE);
            if (bh->b_data == b_data + PAGE_SIZE) {
                  bh->b_size += PAGE_SIZE;
                  bh->b_data -= PAGE_SIZE;
                  if (full)
                        atomic_add(PAGE_SIZE, &bh->b_count);
                  continue;
            }
            if (b_data == bh->b_data + bh->b_size) {
                  bh->b_size += PAGE_SIZE;
                  if (full)
                        atomic_add(PAGE_SIZE, &bh->b_count);
                  continue;
            }
            prev_bh = bh;
            if ((bh = (struct idetape_bh *)kmalloc(sizeof(struct idetape_bh), GFP_KERNEL)) == NULL) {
                  free_page((unsigned long) b_data);
                  goto abort;
            }
            bh->b_reqnext = NULL;
            bh->b_data = b_data;
            bh->b_size = PAGE_SIZE;
            atomic_set(&bh->b_count, full ? bh->b_size : 0);
            prev_bh->b_reqnext = bh;
      }
      bh->b_size -= tape->excess_bh_size;
      if (full)
            atomic_sub(tape->excess_bh_size, &bh->b_count);
      return stage;
abort:
      __idetape_kfree_stage(stage);
      return NULL;
}

static idetape_stage_t *idetape_kmalloc_stage (idetape_tape_t *tape)
{
      idetape_stage_t *cache_stage = tape->cache_stage;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_kmalloc_stage\n");
#endif /* IDETAPE_DEBUG_LOG */

      if (tape->nr_stages >= tape->max_stages)
            return NULL;
      if (cache_stage != NULL) {
            tape->cache_stage = NULL;
            return cache_stage;
      }
      return __idetape_kmalloc_stage(tape, 0, 0);
}

static int idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char __user *buf, int n)
{
      struct idetape_bh *bh = tape->bh;
      int count;
      int ret = 0;

      while (n) {
#if IDETAPE_DEBUG_BUGS
            if (bh == NULL) {
                  printk(KERN_ERR "ide-tape: bh == NULL in "
                        "idetape_copy_stage_from_user\n");
                  return 1;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
            if (copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count))
                  ret = 1;
            n -= count;
            atomic_add(count, &bh->b_count);
            buf += count;
            if (atomic_read(&bh->b_count) == bh->b_size) {
                  bh = bh->b_reqnext;
                  if (bh)
                        atomic_set(&bh->b_count, 0);
            }
      }
      tape->bh = bh;
      return ret;
}

static int idetape_copy_stage_to_user (idetape_tape_t *tape, char __user *buf, idetape_stage_t *stage, int n)
{
      struct idetape_bh *bh = tape->bh;
      int count;
      int ret = 0;

      while (n) {
#if IDETAPE_DEBUG_BUGS
            if (bh == NULL) {
                  printk(KERN_ERR "ide-tape: bh == NULL in "
                        "idetape_copy_stage_to_user\n");
                  return 1;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            count = min(tape->b_count, n);
            if  (copy_to_user(buf, tape->b_data, count))
                  ret = 1;
            n -= count;
            tape->b_data += count;
            tape->b_count -= count;
            buf += count;
            if (!tape->b_count) {
                  tape->bh = bh = bh->b_reqnext;
                  if (bh) {
                        tape->b_data = bh->b_data;
                        tape->b_count = atomic_read(&bh->b_count);
                  }
            }
      }
      return ret;
}

static void idetape_init_merge_stage (idetape_tape_t *tape)
{
      struct idetape_bh *bh = tape->merge_stage->bh;
      
      tape->bh = bh;
      if (tape->chrdev_direction == idetape_direction_write)
            atomic_set(&bh->b_count, 0);
      else {
            tape->b_data = bh->b_data;
            tape->b_count = atomic_read(&bh->b_count);
      }
}

static void idetape_switch_buffers (idetape_tape_t *tape, idetape_stage_t *stage)
{
      struct idetape_bh *tmp;

      tmp = stage->bh;
      stage->bh = tape->merge_stage->bh;
      tape->merge_stage->bh = tmp;
      idetape_init_merge_stage(tape);
}

/*
 *    idetape_add_stage_tail adds a new stage at the end of the pipeline.
 */
static void idetape_add_stage_tail (ide_drive_t *drive,idetape_stage_t *stage)
{
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;
      
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk (KERN_INFO "ide-tape: Reached idetape_add_stage_tail\n");
#endif /* IDETAPE_DEBUG_LOG */
      spin_lock_irqsave(&tape->spinlock, flags);
      stage->next = NULL;
      if (tape->last_stage != NULL)
            tape->last_stage->next=stage;
      else
            tape->first_stage = tape->next_stage=stage;
      tape->last_stage = stage;
      if (tape->next_stage == NULL)
            tape->next_stage = tape->last_stage;
      tape->nr_stages++;
      tape->nr_pending_stages++;
      spin_unlock_irqrestore(&tape->spinlock, flags);
}

/*
 *    idetape_wait_for_request installs a completion in a pending request
 *    and sleeps until it is serviced.
 *
 *    The caller should ensure that the request will not be serviced
 *    before we install the completion (usually by disabling interrupts).
 */
static void idetape_wait_for_request (ide_drive_t *drive, struct request *rq)
{
      DECLARE_COMPLETION(wait);
      idetape_tape_t *tape = drive->driver_data;

#if IDETAPE_DEBUG_BUGS
      if (rq == NULL || (rq->flags & REQ_SPECIAL) == 0) {
            printk (KERN_ERR "ide-tape: bug: Trying to sleep on non-valid request\n");
            return;
      }
#endif /* IDETAPE_DEBUG_BUGS */
      rq->waiting = &wait;
      rq->end_io = blk_end_sync_rq;
      spin_unlock_irq(&tape->spinlock);
      wait_for_completion(&wait);
      /* The stage and its struct request have been deallocated */
      spin_lock_irq(&tape->spinlock);
}

static ide_startstop_t idetape_read_position_callback (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_read_position_result_t *result;
      
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_read_position_callback\n");
#endif /* IDETAPE_DEBUG_LOG */

      if (!tape->pc->error) {
            result = (idetape_read_position_result_t *) tape->pc->buffer;
#if IDETAPE_DEBUG_LOG
            if (tape->debug_level >= 2)
                  printk(KERN_INFO "ide-tape: BOP - %s\n",result->bop ? "Yes":"No");
            if (tape->debug_level >= 2)
                  printk(KERN_INFO "ide-tape: EOP - %s\n",result->eop ? "Yes":"No");
#endif /* IDETAPE_DEBUG_LOG */
            if (result->bpu) {
                  printk(KERN_INFO "ide-tape: Block location is unknown to the tape\n");
                  clear_bit(IDETAPE_ADDRESS_VALID, &tape->flags);
                  idetape_end_request(drive, 0, 0);
            } else {
#if IDETAPE_DEBUG_LOG
                  if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: Block Location - %u\n", ntohl(result->first_block));
#endif /* IDETAPE_DEBUG_LOG */
                  tape->partition = result->partition;
                  tape->first_frame_position = ntohl(result->first_block);
                  tape->last_frame_position = ntohl(result->last_block);
                  tape->blocks_in_buffer = result->blocks_in_buffer[2];
                  set_bit(IDETAPE_ADDRESS_VALID, &tape->flags);
                  idetape_end_request(drive, 1, 0);
            }
      } else {
            idetape_end_request(drive, 0, 0);
      }
      return ide_stopped;
}

/*
 *    idetape_create_write_filemark_cmd will:
 *
 *          1.    Write a filemark if write_filemark=1.
 *          2.    Flush the device buffers without writing a filemark
 *                if write_filemark=0.
 *
 */
static void idetape_create_write_filemark_cmd (ide_drive_t *drive, idetape_pc_t *pc,int write_filemark)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_WRITE_FILEMARK_CMD;
      pc->c[4] = write_filemark;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

static void idetape_create_test_unit_ready_cmd(idetape_pc_t *pc)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_TEST_UNIT_READY_CMD;
      pc->callback = &idetape_pc_callback;
}

/*
 *    idetape_queue_pc_tail is based on the following functions:
 *
 *    ide_do_drive_cmd from ide.c
 *    cdrom_queue_request and cdrom_queue_packet_command from ide-cd.c
 *
 *    We add a special packet command request to the tail of the request
 *    queue, and wait for it to be serviced.
 *
 *    This is not to be called from within the request handling part
 *    of the driver ! We allocate here data in the stack, and it is valid
 *    until the request is finished. This is not the case for the bottom
 *    part of the driver, where we are always leaving the functions to wait
 *    for an interrupt or a timer event.
 *
 *    From the bottom part of the driver, we should allocate safe memory
 *    using idetape_next_pc_storage and idetape_next_rq_storage, and add
 *    the request to the request list without waiting for it to be serviced !
 *    In that case, we usually use idetape_queue_pc_head.
 */
static int __idetape_queue_pc_tail (ide_drive_t *drive, idetape_pc_t *pc)
{
      struct ide_tape_obj *tape = drive->driver_data;
      struct request rq;

      idetape_init_rq(&rq, REQ_IDETAPE_PC1);
      rq.buffer = (char *) pc;
      rq.rq_disk = tape->disk;
      return ide_do_drive_cmd(drive, &rq, ide_wait);
}

static void idetape_create_load_unload_cmd (ide_drive_t *drive, idetape_pc_t *pc,int cmd)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_LOAD_UNLOAD_CMD;
      pc->c[4] = cmd;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

static int idetape_wait_ready(ide_drive_t *drive, unsigned long timeout)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      int load_attempted = 0;

      /*
       * Wait for the tape to become ready
       */
      set_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags);
      timeout += jiffies;
      while (time_before(jiffies, timeout)) {
            idetape_create_test_unit_ready_cmd(&pc);
            if (!__idetape_queue_pc_tail(drive, &pc))
                  return 0;
            if ((tape->sense_key == 2 && tape->asc == 4 && tape->ascq == 2)
                || (tape->asc == 0x3A)) { /* no media */
                  if (load_attempted)
                        return -ENOMEDIUM;
                  idetape_create_load_unload_cmd(drive, &pc, IDETAPE_LU_LOAD_MASK);
                  __idetape_queue_pc_tail(drive, &pc);
                  load_attempted = 1;
            /* not about to be ready */
            } else if (!(tape->sense_key == 2 && tape->asc == 4 &&
                       (tape->ascq == 1 || tape->ascq == 8)))
                  return -EIO;
            msleep(100);
      }
      return -EIO;
}

static int idetape_queue_pc_tail (ide_drive_t *drive,idetape_pc_t *pc)
{
      return __idetape_queue_pc_tail(drive, pc);
}

static int idetape_flush_tape_buffers (ide_drive_t *drive)
{
      idetape_pc_t pc;
      int rc;

      idetape_create_write_filemark_cmd(drive, &pc, 0);
      if ((rc = idetape_queue_pc_tail(drive, &pc)))
            return rc;
      idetape_wait_ready(drive, 60 * 5 * HZ);
      return 0;
}

static void idetape_create_read_position_cmd (idetape_pc_t *pc)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_READ_POSITION_CMD;
      pc->request_transfer = 20;
      pc->callback = &idetape_read_position_callback;
}

static int idetape_read_position (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      int position;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_read_position\n");
#endif /* IDETAPE_DEBUG_LOG */

      idetape_create_read_position_cmd(&pc);
      if (idetape_queue_pc_tail(drive, &pc))
            return -1;
      position = tape->first_frame_position;
      return position;
}

static void idetape_create_locate_cmd (ide_drive_t *drive, idetape_pc_t *pc, unsigned int block, u8 partition, int skip)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_LOCATE_CMD;
      pc->c[1] = 2;
      put_unaligned(htonl(block), (unsigned int *) &pc->c[3]);
      pc->c[8] = partition;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

static int idetape_create_prevent_cmd (ide_drive_t *drive, idetape_pc_t *pc, int prevent)
{
      idetape_tape_t *tape = drive->driver_data;

      if (!tape->capabilities.lock)
            return 0;

      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_PREVENT_CMD;
      pc->c[4] = prevent;
      pc->callback = &idetape_pc_callback;
      return 1;
}

static int __idetape_discard_read_pipeline (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;
      int cnt;

      if (tape->chrdev_direction != idetape_direction_read)
            return 0;

      /* Remove merge stage. */
      cnt = tape->merge_stage_size / tape->tape_block_size;
      if (test_and_clear_bit(IDETAPE_FILEMARK, &tape->flags))
            ++cnt;            /* Filemarks count as 1 sector */
      tape->merge_stage_size = 0;
      if (tape->merge_stage != NULL) {
            __idetape_kfree_stage(tape->merge_stage);
            tape->merge_stage = NULL;
      }

      /* Clear pipeline flags. */
      clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
      tape->chrdev_direction = idetape_direction_none;

      /* Remove pipeline stages. */
      if (tape->first_stage == NULL)
            return 0;

      spin_lock_irqsave(&tape->spinlock, flags);
      tape->next_stage = NULL;
      if (idetape_pipeline_active(tape))
            idetape_wait_for_request(drive, tape->active_data_request);
      spin_unlock_irqrestore(&tape->spinlock, flags);

      while (tape->first_stage != NULL) {
            struct request *rq_ptr = &tape->first_stage->rq;

            cnt += rq_ptr->nr_sectors - rq_ptr->current_nr_sectors; 
            if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
                  ++cnt;
            idetape_remove_stage_head(drive);
      }
      tape->nr_pending_stages = 0;
      tape->max_stages = tape->min_pipeline;
      return cnt;
}

/*
 *    idetape_position_tape positions the tape to the requested block
 *    using the LOCATE packet command. A READ POSITION command is then
 *    issued to check where we are positioned.
 *
 *    Like all higher level operations, we queue the commands at the tail
 *    of the request queue and wait for their completion.
 *    
 */
static int idetape_position_tape (ide_drive_t *drive, unsigned int block, u8 partition, int skip)
{
      idetape_tape_t *tape = drive->driver_data;
      int retval;
      idetape_pc_t pc;

      if (tape->chrdev_direction == idetape_direction_read)
            __idetape_discard_read_pipeline(drive);
      idetape_wait_ready(drive, 60 * 5 * HZ);
      idetape_create_locate_cmd(drive, &pc, block, partition, skip);
      retval = idetape_queue_pc_tail(drive, &pc);
      if (retval)
            return (retval);

      idetape_create_read_position_cmd(&pc);
      return (idetape_queue_pc_tail(drive, &pc));
}

static void idetape_discard_read_pipeline (ide_drive_t *drive, int restore_position)
{
      idetape_tape_t *tape = drive->driver_data;
      int cnt;
      int seek, position;

      cnt = __idetape_discard_read_pipeline(drive);
      if (restore_position) {
            position = idetape_read_position(drive);
            seek = position > cnt ? position - cnt : 0;
            if (idetape_position_tape(drive, seek, 0, 0)) {
                  printk(KERN_INFO "ide-tape: %s: position_tape failed in discard_pipeline()\n", tape->name);
                  return;
            }
      }
}

/*
 * idetape_queue_rw_tail generates a read/write request for the block
 * device interface and wait for it to be serviced.
 */
static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks, struct idetape_bh *bh)
{
      idetape_tape_t *tape = drive->driver_data;
      struct request rq;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 2)
            printk(KERN_INFO "ide-tape: idetape_queue_rw_tail: cmd=%d\n",cmd);
#endif /* IDETAPE_DEBUG_LOG */
#if IDETAPE_DEBUG_BUGS
      if (idetape_pipeline_active(tape)) {
            printk(KERN_ERR "ide-tape: bug: the pipeline is active in idetape_queue_rw_tail\n");
            return (0);
      }
#endif /* IDETAPE_DEBUG_BUGS */     

      idetape_init_rq(&rq, cmd);
      rq.rq_disk = tape->disk;
      rq.special = (void *)bh;
      rq.sector = tape->first_frame_position;
      rq.nr_sectors = rq.current_nr_sectors = blocks;
      (void) ide_do_drive_cmd(drive, &rq, ide_wait);

      if ((cmd & (REQ_IDETAPE_READ | REQ_IDETAPE_WRITE)) == 0)
            return 0;

      if (tape->merge_stage)
            idetape_init_merge_stage(tape);
      if (rq.errors == IDETAPE_ERROR_GENERAL)
            return -EIO;
      return (tape->tape_block_size * (blocks-rq.current_nr_sectors));
}

/*
 *    idetape_insert_pipeline_into_queue is used to start servicing the
 *    pipeline stages, starting from tape->next_stage.
 */
static void idetape_insert_pipeline_into_queue (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

      if (tape->next_stage == NULL)
            return;
      if (!idetape_pipeline_active(tape)) {
            set_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
            idetape_active_next_stage(drive);
            (void) ide_do_drive_cmd(drive, tape->active_data_request, ide_end);
      }
}

static void idetape_create_inquiry_cmd (idetape_pc_t *pc)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_INQUIRY_CMD;
      pc->c[4] = pc->request_transfer = 254;
      pc->callback = &idetape_pc_callback;
}

static void idetape_create_rewind_cmd (ide_drive_t *drive, idetape_pc_t *pc)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_REWIND_CMD;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

#if 0
static void idetape_create_mode_select_cmd (idetape_pc_t *pc, int length)
{
      idetape_init_pc(pc);
      set_bit(PC_WRITING, &pc->flags);
      pc->c[0] = IDETAPE_MODE_SELECT_CMD;
      pc->c[1] = 0x10;
      put_unaligned(htons(length), (unsigned short *) &pc->c[3]);
      pc->request_transfer = 255;
      pc->callback = &idetape_pc_callback;
}
#endif

static void idetape_create_erase_cmd (idetape_pc_t *pc)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_ERASE_CMD;
      pc->c[1] = 1;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

static void idetape_create_space_cmd (idetape_pc_t *pc,int count, u8 cmd)
{
      idetape_init_pc(pc);
      pc->c[0] = IDETAPE_SPACE_CMD;
      put_unaligned(htonl(count), (unsigned int *) &pc->c[1]);
      pc->c[1] = cmd;
      set_bit(PC_WAIT_FOR_DSC, &pc->flags);
      pc->callback = &idetape_pc_callback;
}

static void idetape_wait_first_stage (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;

      if (tape->first_stage == NULL)
            return;
      spin_lock_irqsave(&tape->spinlock, flags);
      if (tape->active_stage == tape->first_stage)
            idetape_wait_for_request(drive, tape->active_data_request);
      spin_unlock_irqrestore(&tape->spinlock, flags);
}

/*
 *    idetape_add_chrdev_write_request tries to add a character device
 *    originated write request to our pipeline. In case we don't succeed,
 *    we revert to non-pipelined operation mode for this request.
 *
 *    1.    Try to allocate a new pipeline stage.
 *    2.    If we can't, wait for more and more requests to be serviced
 *          and try again each time.
 *    3.    If we still can't allocate a stage, fallback to
 *          non-pipelined operation mode for this request.
 */
static int idetape_add_chrdev_write_request (ide_drive_t *drive, int blocks)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *new_stage;
      unsigned long flags;
      struct request *rq;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 3)
            printk(KERN_INFO "ide-tape: Reached idetape_add_chrdev_write_request\n");
#endif /* IDETAPE_DEBUG_LOG */

      /*
       *    Attempt to allocate a new stage.
       *    Pay special attention to possible race conditions.
       */
      while ((new_stage = idetape_kmalloc_stage(tape)) == NULL) {
            spin_lock_irqsave(&tape->spinlock, flags);
            if (idetape_pipeline_active(tape)) {
                  idetape_wait_for_request(drive, tape->active_data_request);
                  spin_unlock_irqrestore(&tape->spinlock, flags);
            } else {
                  spin_unlock_irqrestore(&tape->spinlock, flags);
                  idetape_insert_pipeline_into_queue(drive);
                  if (idetape_pipeline_active(tape))
                        continue;
                  /*
                   *    Linux is short on memory. Fallback to
                   *    non-pipelined operation mode for this request.
                   */
                  return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, blocks, tape->merge_stage->bh);
            }
      }
      rq = &new_stage->rq;
      idetape_init_rq(rq, REQ_IDETAPE_WRITE);
      /* Doesn't actually matter - We always assume sequential access */
      rq->sector = tape->first_frame_position;
      rq->nr_sectors = rq->current_nr_sectors = blocks;

      idetape_switch_buffers(tape, new_stage);
      idetape_add_stage_tail(drive, new_stage);
      tape->pipeline_head++;
#if USE_IOTRACE
      IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
      calculate_speeds(drive);

      /*
       *    Estimate whether the tape has stopped writing by checking
       *    if our write pipeline is currently empty. If we are not
       *    writing anymore, wait for the pipeline to be full enough
       *    (90%) before starting to service requests, so that we will
       *    be able to keep up with the higher speeds of the tape.
       */
      if (!idetape_pipeline_active(tape)) {
            if (tape->nr_stages >= tape->max_stages * 9 / 10 ||
                tape->nr_stages >= tape->max_stages - tape->uncontrolled_pipeline_head_speed * 3 * 1024 / tape->tape_block_size) {
                  tape->measure_insert_time = 1;
                  tape->insert_time = jiffies;
                  tape->insert_size = 0;
                  tape->insert_speed = 0;
                  idetape_insert_pipeline_into_queue(drive);
            }
      }
      if (test_and_clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags))
            /* Return a deferred error */
            return -EIO;
      return blocks;
}

/*
 *    idetape_wait_for_pipeline will wait until all pending pipeline
 *    requests are serviced. Typically called on device close.
 */
static void idetape_wait_for_pipeline (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;

      while (tape->next_stage || idetape_pipeline_active(tape)) {
            idetape_insert_pipeline_into_queue(drive);
            spin_lock_irqsave(&tape->spinlock, flags);
            if (idetape_pipeline_active(tape))
                  idetape_wait_for_request(drive, tape->active_data_request);
            spin_unlock_irqrestore(&tape->spinlock, flags);
      }
}

static void idetape_empty_write_pipeline (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      int blocks, min;
      struct idetape_bh *bh;
      
#if IDETAPE_DEBUG_BUGS
      if (tape->chrdev_direction != idetape_direction_write) {
            printk(KERN_ERR "ide-tape: bug: Trying to empty write pipeline, but we are not writing.\n");
            return;
      }
      if (tape->merge_stage_size > tape->stage_size) {
            printk(KERN_ERR "ide-tape: bug: merge_buffer too big\n");
            tape->merge_stage_size = tape->stage_size;
      }
#endif /* IDETAPE_DEBUG_BUGS */
      if (tape->merge_stage_size) {
            blocks = tape->merge_stage_size / tape->tape_block_size;
            if (tape->merge_stage_size % tape->tape_block_size) {
                  unsigned int i;

                  blocks++;
                  i = tape->tape_block_size - tape->merge_stage_size % tape->tape_block_size;
                  bh = tape->bh->b_reqnext;
                  while (bh) {
                        atomic_set(&bh->b_count, 0);
                        bh = bh->b_reqnext;
                  }
                  bh = tape->bh;
                  while (i) {
                        if (bh == NULL) {

                              printk(KERN_INFO "ide-tape: bug, bh NULL\n");
                              break;
                        }
                        min = min(i, (unsigned int)(bh->b_size - atomic_read(&bh->b_count)));
                        memset(bh->b_data + atomic_read(&bh->b_count), 0, min);
                        atomic_add(min, &bh->b_count);
                        i -= min;
                        bh = bh->b_reqnext;
                  }
            }
            (void) idetape_add_chrdev_write_request(drive, blocks);
            tape->merge_stage_size = 0;
      }
      idetape_wait_for_pipeline(drive);
      if (tape->merge_stage != NULL) {
            __idetape_kfree_stage(tape->merge_stage);
            tape->merge_stage = NULL;
      }
      clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
      tape->chrdev_direction = idetape_direction_none;

      /*
       *    On the next backup, perform the feedback loop again.
       *    (I don't want to keep sense information between backups,
       *     as some systems are constantly on, and the system load
       *     can be totally different on the next backup).
       */
      tape->max_stages = tape->min_pipeline;
#if IDETAPE_DEBUG_BUGS
      if (tape->first_stage != NULL ||
          tape->next_stage != NULL ||
          tape->last_stage != NULL ||
          tape->nr_stages != 0) {
            printk(KERN_ERR "ide-tape: ide-tape pipeline bug, "
                  "first_stage %p, next_stage %p, "
                  "last_stage %p, nr_stages %d\n",
                  tape->first_stage, tape->next_stage,
                  tape->last_stage, tape->nr_stages);
      }
#endif /* IDETAPE_DEBUG_BUGS */
}

static void idetape_restart_speed_control (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

      tape->restart_speed_control_req = 0;
      tape->pipeline_head = 0;
      tape->controlled_last_pipeline_head = tape->uncontrolled_last_pipeline_head = 0;
      tape->controlled_previous_pipeline_head = tape->uncontrolled_previous_pipeline_head = 0;
      tape->pipeline_head_speed = tape->controlled_pipeline_head_speed = 5000;
      tape->uncontrolled_pipeline_head_speed = 0;
      tape->controlled_pipeline_head_time = tape->uncontrolled_pipeline_head_time = jiffies;
      tape->controlled_previous_head_time = tape->uncontrolled_previous_head_time = jiffies;
}

static int idetape_initiate_read (ide_drive_t *drive, int max_stages)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *new_stage;
      struct request rq;
      int bytes_read;
      int blocks = tape->capabilities.ctl;

      /* Initialize read operation */
      if (tape->chrdev_direction != idetape_direction_read) {
            if (tape->chrdev_direction == idetape_direction_write) {
                  idetape_empty_write_pipeline(drive);
                  idetape_flush_tape_buffers(drive);
            }
#if IDETAPE_DEBUG_BUGS
            if (tape->merge_stage || tape->merge_stage_size) {
                  printk (KERN_ERR "ide-tape: merge_stage_size should be 0 now\n");
                  tape->merge_stage_size = 0;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                  return -ENOMEM;
            tape->chrdev_direction = idetape_direction_read;

            /*
             *    Issue a read 0 command to ensure that DSC handshake
             *    is switched from completion mode to buffer available
             *    mode.
             *    No point in issuing this if DSC overlap isn't supported,
             *    some drives (Seagate STT3401A) will return an error.
             */
            if (drive->dsc_overlap) {
                  bytes_read = idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, 0, tape->merge_stage->bh);
                  if (bytes_read < 0) {
                        __idetape_kfree_stage(tape->merge_stage);
                        tape->merge_stage = NULL;
                        tape->chrdev_direction = idetape_direction_none;
                        return bytes_read;
                  }
            }
      }
      if (tape->restart_speed_control_req)
            idetape_restart_speed_control(drive);
      idetape_init_rq(&rq, REQ_IDETAPE_READ);
      rq.sector = tape->first_frame_position;
      rq.nr_sectors = rq.current_nr_sectors = blocks;
      if (!test_bit(IDETAPE_PIPELINE_ERROR, &tape->flags) &&
          tape->nr_stages < max_stages) {
            new_stage = idetape_kmalloc_stage(tape);
            while (new_stage != NULL) {
                  new_stage->rq = rq;
                  idetape_add_stage_tail(drive, new_stage);
                  if (tape->nr_stages >= max_stages)
                        break;
                  new_stage = idetape_kmalloc_stage(tape);
            }
      }
      if (!idetape_pipeline_active(tape)) {
            if (tape->nr_pending_stages >= 3 * max_stages / 4) {
                  tape->measure_insert_time = 1;
                  tape->insert_time = jiffies;
                  tape->insert_size = 0;
                  tape->insert_speed = 0;
                  idetape_insert_pipeline_into_queue(drive);
            }
      }
      return 0;
}

/*
 *    idetape_add_chrdev_read_request is called from idetape_chrdev_read
 *    to service a character device read request and add read-ahead
 *    requests to our pipeline.
 */
static int idetape_add_chrdev_read_request (ide_drive_t *drive,int blocks)
{
      idetape_tape_t *tape = drive->driver_data;
      unsigned long flags;
      struct request *rq_ptr;
      int bytes_read;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_add_chrdev_read_request, %d blocks\n", blocks);
#endif /* IDETAPE_DEBUG_LOG */

      /*
       * If we are at a filemark, return a read length of 0
       */
      if (test_bit(IDETAPE_FILEMARK, &tape->flags))
            return 0;

      /*
       * Wait for the next block to be available at the head
       * of the pipeline
       */
      idetape_initiate_read(drive, tape->max_stages);
      if (tape->first_stage == NULL) {
            if (test_bit(IDETAPE_PIPELINE_ERROR, &tape->flags))
                  return 0;
            return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks, tape->merge_stage->bh);
      }
      idetape_wait_first_stage(drive);
      rq_ptr = &tape->first_stage->rq;
      bytes_read = tape->tape_block_size * (rq_ptr->nr_sectors - rq_ptr->current_nr_sectors);
      rq_ptr->nr_sectors = rq_ptr->current_nr_sectors = 0;


      if (rq_ptr->errors == IDETAPE_ERROR_EOD)
            return 0;
      else {
            idetape_switch_buffers(tape, tape->first_stage);
            if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
                  set_bit(IDETAPE_FILEMARK, &tape->flags);
            spin_lock_irqsave(&tape->spinlock, flags);
            idetape_remove_stage_head(drive);
            spin_unlock_irqrestore(&tape->spinlock, flags);
            tape->pipeline_head++;
#if USE_IOTRACE
            IO_trace(IO_IDETAPE_FIFO, tape->pipeline_head, tape->buffer_head, tape->tape_head, tape->minor);
#endif
            calculate_speeds(drive);
      }
#if IDETAPE_DEBUG_BUGS
      if (bytes_read > blocks * tape->tape_block_size) {
            printk(KERN_ERR "ide-tape: bug: trying to return more bytes than requested\n");
            bytes_read = blocks * tape->tape_block_size;
      }
#endif /* IDETAPE_DEBUG_BUGS */
      return (bytes_read);
}

static void idetape_pad_zeros (ide_drive_t *drive, int bcount)
{
      idetape_tape_t *tape = drive->driver_data;
      struct idetape_bh *bh;
      int blocks;
      
      while (bcount) {
            unsigned int count;

            bh = tape->merge_stage->bh;
            count = min(tape->stage_size, bcount);
            bcount -= count;
            blocks = count / tape->tape_block_size;
            while (count) {
                  atomic_set(&bh->b_count, min(count, (unsigned int)bh->b_size));
                  memset(bh->b_data, 0, atomic_read(&bh->b_count));
                  count -= atomic_read(&bh->b_count);
                  bh = bh->b_reqnext;
            }
            idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, blocks, tape->merge_stage->bh);
      }
}

static int idetape_pipeline_size (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_stage_t *stage;
      struct request *rq;
      int size = 0;

      idetape_wait_for_pipeline(drive);
      stage = tape->first_stage;
      while (stage != NULL) {
            rq = &stage->rq;
            size += tape->tape_block_size * (rq->nr_sectors-rq->current_nr_sectors);
            if (rq->errors == IDETAPE_ERROR_FILEMARK)
                  size += tape->tape_block_size;
            stage = stage->next;
      }
      size += tape->merge_stage_size;
      return size;
}

/*
 *    Rewinds the tape to the Beginning Of the current Partition (BOP).
 *
 *    We currently support only one partition.
 */ 
static int idetape_rewind_tape (ide_drive_t *drive)
{
      int retval;
      idetape_pc_t pc;
#if IDETAPE_DEBUG_LOG
      idetape_tape_t *tape = drive->driver_data;
      if (tape->debug_level >= 2)
            printk(KERN_INFO "ide-tape: Reached idetape_rewind_tape\n");
#endif /* IDETAPE_DEBUG_LOG */      
      
      idetape_create_rewind_cmd(drive, &pc);
      retval = idetape_queue_pc_tail(drive, &pc);
      if (retval)
            return retval;

      idetape_create_read_position_cmd(&pc);
      retval = idetape_queue_pc_tail(drive, &pc);
      if (retval)
            return retval;
      return 0;
}

/*
 *    Our special ide-tape ioctl's.
 *
 *    Currently there aren't any ioctl's.
 *    mtio.h compatible commands should be issued to the character device
 *    interface.
 */
static int idetape_blkdev_ioctl(ide_drive_t *drive, unsigned int cmd, unsigned long arg)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_config_t config;
      void __user *argp = (void __user *)arg;

#if IDETAPE_DEBUG_LOG   
      if (tape->debug_level >= 4)
            printk(KERN_INFO "ide-tape: Reached idetape_blkdev_ioctl\n");
#endif /* IDETAPE_DEBUG_LOG */
      switch (cmd) {
            case 0x0340:
                  if (copy_from_user(&config, argp, sizeof (idetape_config_t)))
                        return -EFAULT;
                  tape->best_dsc_rw_frequency = config.dsc_rw_frequency;
                  tape->max_stages = config.nr_stages;
                  break;
            case 0x0350:
                  config.dsc_rw_frequency = (int) tape->best_dsc_rw_frequency;
                  config.nr_stages = tape->max_stages; 
                  if (copy_to_user(argp, &config, sizeof (idetape_config_t)))
                        return -EFAULT;
                  break;
            default:
                  return -EIO;
      }
      return 0;
}

/*
 *    idetape_space_over_filemarks is now a bit more complicated than just
 *    passing the command to the tape since we may have crossed some
 *    filemarks during our pipelined read-ahead mode.
 *
 *    As a minor side effect, the pipeline enables us to support MTFSFM when
 *    the filemark is in our internal pipeline even if the tape doesn't
 *    support spacing over filemarks in the reverse direction.
 */
static int idetape_space_over_filemarks (ide_drive_t *drive,short mt_op,int mt_count)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      unsigned long flags;
      int retval,count=0;

      if (mt_count == 0)
            return 0;
      if (MTBSF == mt_op || MTBSFM == mt_op) {
            if (!tape->capabilities.sprev)
                  return -EIO;
            mt_count = - mt_count;
      }

      if (tape->chrdev_direction == idetape_direction_read) {
            /*
             *    We have a read-ahead buffer. Scan it for crossed
             *    filemarks.
             */
            tape->merge_stage_size = 0;
            if (test_and_clear_bit(IDETAPE_FILEMARK, &tape->flags))
                  ++count;
            while (tape->first_stage != NULL) {
                  if (count == mt_count) {
                        if (mt_op == MTFSFM)
                              set_bit(IDETAPE_FILEMARK, &tape->flags);
                        return 0;
                  }
                  spin_lock_irqsave(&tape->spinlock, flags);
                  if (tape->first_stage == tape->active_stage) {
                        /*
                         *    We have reached the active stage in the read pipeline.
                         *    There is no point in allowing the drive to continue
                         *    reading any farther, so we stop the pipeline.
                         *
                         *    This section should be moved to a separate subroutine,
                         *    because a similar function is performed in
                         *    __idetape_discard_read_pipeline(), for example.
                         */
                        tape->next_stage = NULL;
                        spin_unlock_irqrestore(&tape->spinlock, flags);
                        idetape_wait_first_stage(drive);
                        tape->next_stage = tape->first_stage->next;
                  } else
                        spin_unlock_irqrestore(&tape->spinlock, flags);
                  if (tape->first_stage->rq.errors == IDETAPE_ERROR_FILEMARK)
                        ++count;
                  idetape_remove_stage_head(drive);
            }
            idetape_discard_read_pipeline(drive, 0);
      }

      /*
       *    The filemark was not found in our internal pipeline.
       *    Now we can issue the space command.
       */
      switch (mt_op) {
            case MTFSF:
            case MTBSF:
                  idetape_create_space_cmd(&pc,mt_count-count,IDETAPE_SPACE_OVER_FILEMARK);
                  return (idetape_queue_pc_tail(drive, &pc));
            case MTFSFM:
            case MTBSFM:
                  if (!tape->capabilities.sprev)
                        return (-EIO);
                  retval = idetape_space_over_filemarks(drive, MTFSF, mt_count-count);
                  if (retval) return (retval);
                  count = (MTBSFM == mt_op ? 1 : -1);
                  return (idetape_space_over_filemarks(drive, MTFSF, count));
            default:
                  printk(KERN_ERR "ide-tape: MTIO operation %d not supported\n",mt_op);
                  return (-EIO);
      }
}


/*
 *    Our character device read / write functions.
 *
 *    The tape is optimized to maximize throughput when it is transferring
 *    an integral number of the "continuous transfer limit", which is
 *    a parameter of the specific tape (26 KB on my particular tape).
 *      (32 kB for Onstream)
 *
 *    As of version 1.3 of the driver, the character device provides an
 *    abstract continuous view of the media - any mix of block sizes (even 1
 *    byte) on the same backup/restore procedure is supported. The driver
 *    will internally convert the requests to the recommended transfer unit,
 *    so that an unmatch between the user's block size to the recommended
 *    size will only result in a (slightly) increased driver overhead, but
 *    will no longer hit performance.
 *      This is not applicable to Onstream.
 */
static ssize_t idetape_chrdev_read (struct file *file, char __user *buf,
                            size_t count, loff_t *ppos)
{
      struct ide_tape_obj *tape = ide_tape_f(file);
      ide_drive_t *drive = tape->drive;
      ssize_t bytes_read,temp, actually_read = 0, rc;
      ssize_t ret = 0;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 3)
            printk(KERN_INFO "ide-tape: Reached idetape_chrdev_read, count %Zd\n", count);
#endif /* IDETAPE_DEBUG_LOG */

      if (tape->chrdev_direction != idetape_direction_read) {
            if (test_bit(IDETAPE_DETECT_BS, &tape->flags))
                  if (count > tape->tape_block_size &&
                      (count % tape->tape_block_size) == 0)
                        tape->user_bs_factor = count / tape->tape_block_size;
      }
      if ((rc = idetape_initiate_read(drive, tape->max_stages)) < 0)
            return rc;
      if (count == 0)
            return (0);
      if (tape->merge_stage_size) {
            actually_read = min((unsigned int)(tape->merge_stage_size), (unsigned int)count);
            if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, actually_read))
                  ret = -EFAULT;
            buf += actually_read;
            tape->merge_stage_size -= actually_read;
            count -= actually_read;
      }
      while (count >= tape->stage_size) {
            bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
            if (bytes_read <= 0)
                  goto finish;
            if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, bytes_read))
                  ret = -EFAULT;
            buf += bytes_read;
            count -= bytes_read;
            actually_read += bytes_read;
      }
      if (count) {
            bytes_read = idetape_add_chrdev_read_request(drive, tape->capabilities.ctl);
            if (bytes_read <= 0)
                  goto finish;
            temp = min((unsigned long)count, (unsigned long)bytes_read);
            if (idetape_copy_stage_to_user(tape, buf, tape->merge_stage, temp))
                  ret = -EFAULT;
            actually_read += temp;
            tape->merge_stage_size = bytes_read-temp;
      }
finish:
      if (!actually_read && test_bit(IDETAPE_FILEMARK, &tape->flags)) {
#if IDETAPE_DEBUG_LOG
            if (tape->debug_level >= 2)
                  printk(KERN_INFO "ide-tape: %s: spacing over filemark\n", tape->name);
#endif
            idetape_space_over_filemarks(drive, MTFSF, 1);
            return 0;
      }

      return (ret) ? ret : actually_read;
}

static ssize_t idetape_chrdev_write (struct file *file, const char __user *buf,
                             size_t count, loff_t *ppos)
{
      struct ide_tape_obj *tape = ide_tape_f(file);
      ide_drive_t *drive = tape->drive;
      ssize_t actually_written = 0;
      ssize_t ret = 0;

      /* The drive is write protected. */
      if (tape->write_prot)
            return -EACCES;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 3)
            printk(KERN_INFO "ide-tape: Reached idetape_chrdev_write, "
                  "count %Zd\n", count);
#endif /* IDETAPE_DEBUG_LOG */

      /* Initialize write operation */
      if (tape->chrdev_direction != idetape_direction_write) {
            if (tape->chrdev_direction == idetape_direction_read)
                  idetape_discard_read_pipeline(drive, 1);
#if IDETAPE_DEBUG_BUGS
            if (tape->merge_stage || tape->merge_stage_size) {
                  printk(KERN_ERR "ide-tape: merge_stage_size "
                        "should be 0 now\n");
                  tape->merge_stage_size = 0;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                  return -ENOMEM;
            tape->chrdev_direction = idetape_direction_write;
            idetape_init_merge_stage(tape);

            /*
             *    Issue a write 0 command to ensure that DSC handshake
             *    is switched from completion mode to buffer available
             *    mode.
             *    No point in issuing this if DSC overlap isn't supported,
             *    some drives (Seagate STT3401A) will return an error.
             */
            if (drive->dsc_overlap) {
                  ssize_t retval = idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, 0, tape->merge_stage->bh);
                  if (retval < 0) {
                        __idetape_kfree_stage(tape->merge_stage);
                        tape->merge_stage = NULL;
                        tape->chrdev_direction = idetape_direction_none;
                        return retval;
                  }
            }
      }
      if (count == 0)
            return (0);
      if (tape->restart_speed_control_req)
            idetape_restart_speed_control(drive);
      if (tape->merge_stage_size) {
#if IDETAPE_DEBUG_BUGS
            if (tape->merge_stage_size >= tape->stage_size) {
                  printk(KERN_ERR "ide-tape: bug: merge buffer too big\n");
                  tape->merge_stage_size = 0;
            }
#endif /* IDETAPE_DEBUG_BUGS */
            actually_written = min((unsigned int)(tape->stage_size - tape->merge_stage_size), (unsigned int)count);
            if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, actually_written))
                        ret = -EFAULT;
            buf += actually_written;
            tape->merge_stage_size += actually_written;
            count -= actually_written;

            if (tape->merge_stage_size == tape->stage_size) {
                  ssize_t retval;
                  tape->merge_stage_size = 0;
                  retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
                  if (retval <= 0)
                        return (retval);
            }
      }
      while (count >= tape->stage_size) {
            ssize_t retval;
            if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, tape->stage_size))
                  ret = -EFAULT;
            buf += tape->stage_size;
            count -= tape->stage_size;
            retval = idetape_add_chrdev_write_request(drive, tape->capabilities.ctl);
            actually_written += tape->stage_size;
            if (retval <= 0)
                  return (retval);
      }
      if (count) {
            actually_written += count;
            if (idetape_copy_stage_from_user(tape, tape->merge_stage, buf, count))
                  ret = -EFAULT;
            tape->merge_stage_size += count;
      }
      return (ret) ? ret : actually_written;
}

static int idetape_write_filemark (ide_drive_t *drive)
{
      idetape_pc_t pc;

      /* Write a filemark */
      idetape_create_write_filemark_cmd(drive, &pc, 1);
      if (idetape_queue_pc_tail(drive, &pc)) {
            printk(KERN_ERR "ide-tape: Couldn't write a filemark\n");
            return -EIO;
      }
      return 0;
}

/*
 *    idetape_mtioctop is called from idetape_chrdev_ioctl when
 *    the general mtio MTIOCTOP ioctl is requested.
 *
 *    We currently support the following mtio.h operations:
 *
 *    MTFSF -     Space over mt_count filemarks in the positive direction.
 *                The tape is positioned after the last spaced filemark.
 *
 *    MTFSFM      -     Same as MTFSF, but the tape is positioned before the
 *                last filemark.
 *
 *    MTBSF -     Steps background over mt_count filemarks, tape is
 *                positioned before the last filemark.
 *
 *    MTBSFM      -     Like MTBSF, only tape is positioned after the last filemark.
 *
 *    Note:
 *
 *          MTBSF and MTBSFM are not supported when the tape doesn't
 *          support spacing over filemarks in the reverse direction.
 *          In this case, MTFSFM is also usually not supported (it is
 *          supported in the rare case in which we crossed the filemark
 *          during our read-ahead pipelined operation mode).
 *          
 *    MTWEOF      -     Writes mt_count filemarks. Tape is positioned after
 *                the last written filemark.
 *
 *    MTREW -     Rewinds tape.
 *
 *    MTLOAD      -     Loads the tape.
 *
 *    MTOFFL      -     Puts the tape drive "Offline": Rewinds the tape and
 *    MTUNLOAD    prevents further access until the media is replaced.
 *
 *    MTNOP -     Flushes tape buffers.
 *
 *    MTRETEN     -     Retension media. This typically consists of one end
 *                to end pass on the media.
 *
 *    MTEOM -     Moves to the end of recorded data.
 *
 *    MTERASE     -     Erases tape.
 *
 *    MTSETBLK -  Sets the user block size to mt_count bytes. If
 *                mt_count is 0, we will attempt to autodetect
 *                the block size.
 *
 *    MTSEEK      -     Positions the tape in a specific block number, where
 *                each block is assumed to contain which user_block_size
 *                bytes.
 *
 *    MTSETPART -       Switches to another tape partition.
 *
 *    MTLOCK -    Locks the tape door.
 *
 *    MTUNLOCK -  Unlocks the tape door.
 *
 *    The following commands are currently not supported:
 *
 *    MTFSS, MTBSS, MTWSM, MTSETDENSITY,
 *    MTSETDRVBUFFER, MT_ST_BOOLEANS, MT_ST_WRITE_THRESHOLD.
 */
static int idetape_mtioctop (ide_drive_t *drive,short mt_op,int mt_count)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      int i,retval;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 1)
            printk(KERN_INFO "ide-tape: Handling MTIOCTOP ioctl: "
                  "mt_op=%d, mt_count=%d\n", mt_op, mt_count);
#endif /* IDETAPE_DEBUG_LOG */
      /*
       *    Commands which need our pipelined read-ahead stages.
       */
      switch (mt_op) {
            case MTFSF:
            case MTFSFM:
            case MTBSF:
            case MTBSFM:
                  if (!mt_count)
                        return (0);
                  return (idetape_space_over_filemarks(drive,mt_op,mt_count));
            default:
                  break;
      }
      switch (mt_op) {
            case MTWEOF:
                  if (tape->write_prot)
                        return -EACCES;
                  idetape_discard_read_pipeline(drive, 1);
                  for (i = 0; i < mt_count; i++) {
                        retval = idetape_write_filemark(drive);
                        if (retval)
                              return retval;
                  }
                  return (0);
            case MTREW:
                  idetape_discard_read_pipeline(drive, 0);
                  if (idetape_rewind_tape(drive))
                        return -EIO;
                  return 0;
            case MTLOAD:
                  idetape_discard_read_pipeline(drive, 0);
                  idetape_create_load_unload_cmd(drive, &pc, IDETAPE_LU_LOAD_MASK);
                  return (idetape_queue_pc_tail(drive, &pc));
            case MTUNLOAD:
            case MTOFFL:
                  /*
                   * If door is locked, attempt to unlock before
                   * attempting to eject.
                   */
                  if (tape->door_locked) {
                        if (idetape_create_prevent_cmd(drive, &pc, 0))
                              if (!idetape_queue_pc_tail(drive, &pc))
                                    tape->door_locked = DOOR_UNLOCKED;
                  }
                  idetape_discard_read_pipeline(drive, 0);
                  idetape_create_load_unload_cmd(drive, &pc,!IDETAPE_LU_LOAD_MASK);
                  retval = idetape_queue_pc_tail(drive, &pc);
                  if (!retval)
                        clear_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags);
                  return retval;
            case MTNOP:
                  idetape_discard_read_pipeline(drive, 0);
                  return (idetape_flush_tape_buffers(drive));
            case MTRETEN:
                  idetape_discard_read_pipeline(drive, 0);
                  idetape_create_load_unload_cmd(drive, &pc,IDETAPE_LU_RETENSION_MASK | IDETAPE_LU_LOAD_MASK);
                  return (idetape_queue_pc_tail(drive, &pc));
            case MTEOM:
                  idetape_create_space_cmd(&pc, 0, IDETAPE_SPACE_TO_EOD);
                  return (idetape_queue_pc_tail(drive, &pc));
            case MTERASE:
                  (void) idetape_rewind_tape(drive);
                  idetape_create_erase_cmd(&pc);
                  return (idetape_queue_pc_tail(drive, &pc));
            case MTSETBLK:
                  if (mt_count) {
                        if (mt_count < tape->tape_block_size || mt_count % tape->tape_block_size)
                              return -EIO;
                        tape->user_bs_factor = mt_count / tape->tape_block_size;
                        clear_bit(IDETAPE_DETECT_BS, &tape->flags);
                  } else
                        set_bit(IDETAPE_DETECT_BS, &tape->flags);
                  return 0;
            case MTSEEK:
                  idetape_discard_read_pipeline(drive, 0);
                  return idetape_position_tape(drive, mt_count * tape->user_bs_factor, tape->partition, 0);
            case MTSETPART:
                  idetape_discard_read_pipeline(drive, 0);
                  return (idetape_position_tape(drive, 0, mt_count, 0));
            case MTFSR:
            case MTBSR:
            case MTLOCK:
                  if (!idetape_create_prevent_cmd(drive, &pc, 1))
                        return 0;
                  retval = idetape_queue_pc_tail(drive, &pc);
                  if (retval) return retval;
                  tape->door_locked = DOOR_EXPLICITLY_LOCKED;
                  return 0;
            case MTUNLOCK:
                  if (!idetape_create_prevent_cmd(drive, &pc, 0))
                        return 0;
                  retval = idetape_queue_pc_tail(drive, &pc);
                  if (retval) return retval;
                  tape->door_locked = DOOR_UNLOCKED;
                  return 0;
            default:
                  printk(KERN_ERR "ide-tape: MTIO operation %d not "
                        "supported\n", mt_op);
                  return (-EIO);
      }
}

/*
 *    Our character device ioctls.
 *
 *    General mtio.h magnetic io commands are supported here, and not in
 *    the corresponding block interface.
 *
 *    The following ioctls are supported:
 *
 *    MTIOCTOP -  Refer to idetape_mtioctop for detailed description.
 *
 *    MTIOCGET -  The mt_dsreg field in the returned mtget structure
 *                will be set to (user block size in bytes <<
 *                MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK.
 *
 *                The mt_blkno is set to the current user block number.
 *                The other mtget fields are not supported.
 *
 *    MTIOCPOS -  The current tape "block position" is returned. We
 *                assume that each block contains user_block_size
 *                bytes.
 *
 *    Our own ide-tape ioctls are supported on both interfaces.
 */
static int idetape_chrdev_ioctl (struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
      struct ide_tape_obj *tape = ide_tape_f(file);
      ide_drive_t *drive = tape->drive;
      struct mtop mtop;
      struct mtget mtget;
      struct mtpos mtpos;
      int block_offset = 0, position = tape->first_frame_position;
      void __user *argp = (void __user *)arg;

#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 3)
            printk(KERN_INFO "ide-tape: Reached idetape_chrdev_ioctl, "
                  "cmd=%u\n", cmd);
#endif /* IDETAPE_DEBUG_LOG */

      tape->restart_speed_control_req = 1;
      if (tape->chrdev_direction == idetape_direction_write) {
            idetape_empty_write_pipeline(drive);
            idetape_flush_tape_buffers(drive);
      }
      if (cmd == MTIOCGET || cmd == MTIOCPOS) {
            block_offset = idetape_pipeline_size(drive) / (tape->tape_block_size * tape->user_bs_factor);
            if ((position = idetape_read_position(drive)) < 0)
                  return -EIO;
      }
      switch (cmd) {
            case MTIOCTOP:
                  if (copy_from_user(&mtop, argp, sizeof (struct mtop)))
                        return -EFAULT;
                  return (idetape_mtioctop(drive,mtop.mt_op,mtop.mt_count));
            case MTIOCGET:
                  memset(&mtget, 0, sizeof (struct mtget));
                  mtget.mt_type = MT_ISSCSI2;
                  mtget.mt_blkno = position / tape->user_bs_factor - block_offset;
                  mtget.mt_dsreg = ((tape->tape_block_size * tape->user_bs_factor) << MT_ST_BLKSIZE_SHIFT) & MT_ST_BLKSIZE_MASK;
                  if (tape->drv_write_prot) {
                        mtget.mt_gstat |= GMT_WR_PROT(0xffffffff);
                  }
                  if (copy_to_user(argp, &mtget, sizeof(struct mtget)))
                        return -EFAULT;
                  return 0;
            case MTIOCPOS:
                  mtpos.mt_blkno = position / tape->user_bs_factor - block_offset;
                  if (copy_to_user(argp, &mtpos, sizeof(struct mtpos)))
                        return -EFAULT;
                  return 0;
            default:
                  if (tape->chrdev_direction == idetape_direction_read)
                        idetape_discard_read_pipeline(drive, 1);
                  return idetape_blkdev_ioctl(drive, cmd, arg);
      }
}

static void idetape_get_blocksize_from_block_descriptor(ide_drive_t *drive);

/*
 *    Our character device open function.
 */
static int idetape_chrdev_open (struct inode *inode, struct file *filp)
{
      unsigned int minor = iminor(inode), i = minor & ~0xc0;
      ide_drive_t *drive;
      idetape_tape_t *tape;
      idetape_pc_t pc;
      int retval;

      /*
       * We really want to do nonseekable_open(inode, filp); here, but some
       * versions of tar incorrectly call lseek on tapes and bail out if that
       * fails.  So we disallow pread() and pwrite(), but permit lseeks.
       */
      filp->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);

#if IDETAPE_DEBUG_LOG
      printk(KERN_INFO "ide-tape: Reached idetape_chrdev_open\n");
#endif /* IDETAPE_DEBUG_LOG */
      
      if (i >= MAX_HWIFS * MAX_DRIVES)
            return -ENXIO;

      if (!(tape = ide_tape_chrdev_get(i)))
            return -ENXIO;

      drive = tape->drive;

      filp->private_data = tape;

      if (test_and_set_bit(IDETAPE_BUSY, &tape->flags)) {
            retval = -EBUSY;
            goto out_put_tape;
      }

      retval = idetape_wait_ready(drive, 60 * HZ);
      if (retval) {
            clear_bit(IDETAPE_BUSY, &tape->flags);
            printk(KERN_ERR "ide-tape: %s: drive not ready\n", tape->name);
            goto out_put_tape;
      }

      idetape_read_position(drive);
      if (!test_bit(IDETAPE_ADDRESS_VALID, &tape->flags))
            (void)idetape_rewind_tape(drive);

      if (tape->chrdev_direction != idetape_direction_read)
            clear_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);

      /* Read block size and write protect status from drive. */
      idetape_get_blocksize_from_block_descriptor(drive);

      /* Set write protect flag if device is opened as read-only. */
      if ((filp->f_flags & O_ACCMODE) == O_RDONLY)
            tape->write_prot = 1;
      else
            tape->write_prot = tape->drv_write_prot;

      /* Make sure drive isn't write protected if user wants to write. */
      if (tape->write_prot) {
            if ((filp->f_flags & O_ACCMODE) == O_WRONLY ||
                (filp->f_flags & O_ACCMODE) == O_RDWR) {
                  clear_bit(IDETAPE_BUSY, &tape->flags);
                  retval = -EROFS;
                  goto out_put_tape;
            }
      }

      /*
       * Lock the tape drive door so user can't eject.
       */
      if (tape->chrdev_direction == idetape_direction_none) {
            if (idetape_create_prevent_cmd(drive, &pc, 1)) {
                  if (!idetape_queue_pc_tail(drive, &pc)) {
                        if (tape->door_locked != DOOR_EXPLICITLY_LOCKED)
                              tape->door_locked = DOOR_LOCKED;
                  }
            }
      }
      idetape_restart_speed_control(drive);
      tape->restart_speed_control_req = 0;
      return 0;

out_put_tape:
      ide_tape_put(tape);
      return retval;
}

static void idetape_write_release (ide_drive_t *drive, unsigned int minor)
{
      idetape_tape_t *tape = drive->driver_data;

      idetape_empty_write_pipeline(drive);
      tape->merge_stage = __idetape_kmalloc_stage(tape, 1, 0);
      if (tape->merge_stage != NULL) {
            idetape_pad_zeros(drive, tape->tape_block_size * (tape->user_bs_factor - 1));
            __idetape_kfree_stage(tape->merge_stage);
            tape->merge_stage = NULL;
      }
      idetape_write_filemark(drive);
      idetape_flush_tape_buffers(drive);
      idetape_flush_tape_buffers(drive);
}

/*
 *    Our character device release function.
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp)
{
      struct ide_tape_obj *tape = ide_tape_f(filp);
      ide_drive_t *drive = tape->drive;
      idetape_pc_t pc;
      unsigned int minor = iminor(inode);

      lock_kernel();
      tape = drive->driver_data;
#if IDETAPE_DEBUG_LOG
      if (tape->debug_level >= 3)
            printk(KERN_INFO "ide-tape: Reached idetape_chrdev_release\n");
#endif /* IDETAPE_DEBUG_LOG */

      if (tape->chrdev_direction == idetape_direction_write)
            idetape_write_release(drive, minor);
      if (tape->chrdev_direction == idetape_direction_read) {
            if (minor < 128)
                  idetape_discard_read_pipeline(drive, 1);
            else
                  idetape_wait_for_pipeline(drive);
      }
      if (tape->cache_stage != NULL) {
            __idetape_kfree_stage(tape->cache_stage);
            tape->cache_stage = NULL;
      }
      if (minor < 128 && test_bit(IDETAPE_MEDIUM_PRESENT, &tape->flags))
            (void) idetape_rewind_tape(drive);
      if (tape->chrdev_direction == idetape_direction_none) {
            if (tape->door_locked == DOOR_LOCKED) {
                  if (idetape_create_prevent_cmd(drive, &pc, 0)) {
                        if (!idetape_queue_pc_tail(drive, &pc))
                              tape->door_locked = DOOR_UNLOCKED;
                  }
            }
      }
      clear_bit(IDETAPE_BUSY, &tape->flags);
      ide_tape_put(tape);
      unlock_kernel();
      return 0;
}

/*
 *    idetape_identify_device is called to check the contents of the
 *    ATAPI IDENTIFY command results. We return:
 *
 *    1     If the tape can be supported by us, based on the information
 *          we have so far.
 *
 *    0     If this tape driver is not currently supported by us.
 */
static int idetape_identify_device (ide_drive_t *drive)
{
      struct idetape_id_gcw gcw;
      struct hd_driveid *id = drive->id;
#if IDETAPE_DEBUG_INFO
      unsigned short mask,i;
#endif /* IDETAPE_DEBUG_INFO */

      if (drive->id_read == 0)
            return 1;

      *((unsigned short *) &gcw) = id->config;

#if IDETAPE_DEBUG_INFO
      printk(KERN_INFO "ide-tape: Dumping ATAPI Identify Device tape parameters\n");
      printk(KERN_INFO "ide-tape: Protocol Type: ");
      switch (gcw.protocol) {
            case 0: case 1: printk("ATA\n");break;
            case 2:     printk("ATAPI\n");break;
            case 3: printk("Reserved (Unknown to ide-tape)\n");break;
      }
      printk(KERN_INFO "ide-tape: Device Type: %x - ",gcw.device_type); 
      switch (gcw.device_type) {
            case 0: printk("Direct-access Device\n");break;
            case 1: printk("Streaming Tape Device\n");break;
            case 2: case 3: case 4: printk("Reserved\n");break;
            case 5: printk("CD-ROM Device\n");break;
            case 6: printk("Reserved\n");
            case 7: printk("Optical memory Device\n");break;
            case 0x1f: printk("Unknown or no Device type\n");break;
            default: printk("Reserved\n");
      }
      printk(KERN_INFO "ide-tape: Removable: %s",gcw.removable ? "Yes\n":"No\n");   
      printk(KERN_INFO "ide-tape: Command Packet DRQ Type: ");
      switch (gcw.drq_type) {
            case 0: printk("Microprocessor DRQ\n");break;
            case 1: printk("Interrupt DRQ\n");break;
            case 2: printk("Accelerated DRQ\n");break;
            case 3: printk("Reserved\n");break;
      }
      printk(KERN_INFO "ide-tape: Command Packet Size: ");
      switch (gcw.packet_size) {
            case 0: printk("12 bytes\n");break;
            case 1: printk("16 bytes\n");break;
            default: printk("Reserved\n");break;
      }
      printk(KERN_INFO "ide-tape: Model: %.40s\n",id->model);
      printk(KERN_INFO "ide-tape: Firmware Revision: %.8s\n",id->fw_rev);
      printk(KERN_INFO "ide-tape: Serial Number: %.20s\n",id->serial_no);
      printk(KERN_INFO "ide-tape: Write buffer size: %d bytes\n",id->buf_size*512);
      printk(KERN_INFO "ide-tape: DMA: %s",id->capability & 0x01 ? "Yes\n":"No\n");
      printk(KERN_INFO "ide-tape: LBA: %s",id->capability & 0x02 ? "Yes\n":"No\n");
      printk(KERN_INFO "ide-tape: IORDY can be disabled: %s",id->capability & 0x04 ? "Yes\n":"No\n");
      printk(KERN_INFO "ide-tape: IORDY supported: %s",id->capability & 0x08 ? "Yes\n":"Unknown\n");
      printk(KERN_INFO "ide-tape: ATAPI overlap supported: %s",id->capability & 0x20 ? "Yes\n":"No\n");
      printk(KERN_INFO "ide-tape: PIO Cycle Timing Category: %d\n",id->tPIO);
      printk(KERN_INFO "ide-tape: DMA Cycle Timing Category: %d\n",id->tDMA);
      printk(KERN_INFO "ide-tape: Single Word DMA supported modes: ");
      for (i=0,mask=1;i<8;i++,mask=mask << 1) {
            if (id->dma_1word & mask)
                  printk("%d ",i);
            if (id->dma_1word & (mask << 8))
                  printk("(active) ");
      }
      printk("\n");
      printk(KERN_INFO "ide-tape: Multi Word DMA supported modes: ");
      for (i=0,mask=1;i<8;i++,mask=mask << 1) {
            if (id->dma_mword & mask)
                  printk("%d ",i);
            if (id->dma_mword & (mask << 8))
                  printk("(active) ");
      }
      printk("\n");
      if (id->field_valid & 0x0002) {
            printk(KERN_INFO "ide-tape: Enhanced PIO Modes: %s\n",
                  id->eide_pio_modes & 1 ? "Mode 3":"None");
            printk(KERN_INFO "ide-tape: Minimum Multi-word DMA cycle per word: ");
            if (id->eide_dma_min == 0)
                  printk("Not supported\n");
            else
                  printk("%d ns\n",id->eide_dma_min);

            printk(KERN_INFO "ide-tape: Manufacturer\'s Recommended Multi-word cycle: ");
            if (id->eide_dma_time == 0)
                  printk("Not supported\n");
            else
                  printk("%d ns\n",id->eide_dma_time);

            printk(KERN_INFO "ide-tape: Minimum PIO cycle without IORDY: ");
            if (id->eide_pio == 0)
                  printk("Not supported\n");
            else
                  printk("%d ns\n",id->eide_pio);

            printk(KERN_INFO "ide-tape: Minimum PIO cycle with IORDY: ");
            if (id->eide_pio_iordy == 0)
                  printk("Not supported\n");
            else
                  printk("%d ns\n",id->eide_pio_iordy);
            
      } else
            printk(KERN_INFO "ide-tape: According to the device, fields 64-70 are not valid.\n");
#endif /* IDETAPE_DEBUG_INFO */

      /* Check that we can support this device */

      if (gcw.protocol !=2 )
            printk(KERN_ERR "ide-tape: Protocol is not ATAPI\n");
      else if (gcw.device_type != 1)
            printk(KERN_ERR "ide-tape: Device type is not set to tape\n");
      else if (!gcw.removable)
            printk(KERN_ERR "ide-tape: The removable flag is not set\n");
      else if (gcw.packet_size != 0) {
            printk(KERN_ERR "ide-tape: Packet size is not 12 bytes long\n");
            if (gcw.packet_size == 1)
                  printk(KERN_ERR "ide-tape: Sorry, padding to 16 bytes is still not supported\n");
      } else
            return 1;
      return 0;
}

/*
 * Use INQUIRY to get the firmware revision
 */
static void idetape_get_inquiry_results (ide_drive_t *drive)
{
      char *r;
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      idetape_inquiry_result_t *inquiry;
      
      idetape_create_inquiry_cmd(&pc);
      if (idetape_queue_pc_tail(drive, &pc)) {
            printk(KERN_ERR "ide-tape: %s: can't get INQUIRY results\n", tape->name);
            return;
      }
      inquiry = (idetape_inquiry_result_t *) pc.buffer;
      memcpy(tape->vendor_id, inquiry->vendor_id, 8);
      memcpy(tape->product_id, inquiry->product_id, 16);
      memcpy(tape->firmware_revision, inquiry->revision_level, 4);
      ide_fixstring(tape->vendor_id, 10, 0);
      ide_fixstring(tape->product_id, 18, 0);
      ide_fixstring(tape->firmware_revision, 6, 0);
      r = tape->firmware_revision;
      if (*(r + 1) == '.')
            tape->firmware_revision_num = (*r - '0') * 100 + (*(r + 2) - '0') * 10 + *(r + 3) - '0';
      printk(KERN_INFO "ide-tape: %s <-> %s: %s %s rev %s\n", drive->name, tape->name, tape->vendor_id, tape->product_id, tape->firmware_revision);
}

/*
 *    idetape_get_mode_sense_results asks the tape about its various
 *    parameters. In particular, we will adjust our data transfer buffer
 *    size to the recommended value as returned by the tape.
 */
static void idetape_get_mode_sense_results (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      idetape_mode_parameter_header_t *header;
      idetape_capabilities_page_t *capabilities;
      
      idetape_create_mode_sense_cmd(&pc, IDETAPE_CAPABILITIES_PAGE);
      if (idetape_queue_pc_tail(drive, &pc)) {
            printk(KERN_ERR "ide-tape: Can't get tape parameters - assuming some default values\n");
            tape->tape_block_size = 512;
            tape->capabilities.ctl = 52;
            tape->capabilities.speed = 450;
            tape->capabilities.buffer_size = 6 * 52;
            return;
      }
      header = (idetape_mode_parameter_header_t *) pc.buffer;
      capabilities = (idetape_capabilities_page_t *) (pc.buffer + sizeof(idetape_mode_parameter_header_t) + header->bdl);

      capabilities->max_speed = ntohs(capabilities->max_speed);
      capabilities->ctl = ntohs(capabilities->ctl);
      capabilities->speed = ntohs(capabilities->speed);
      capabilities->buffer_size = ntohs(capabilities->buffer_size);

      if (!capabilities->speed) {
            printk(KERN_INFO "ide-tape: %s: overriding capabilities->speed (assuming 650KB/sec)\n", drive->name);
            capabilities->speed = 650;
      }
      if (!capabilities->max_speed) {
            printk(KERN_INFO "ide-tape: %s: overriding capabilities->max_speed (assuming 650KB/sec)\n", drive->name);
            capabilities->max_speed = 650;
      }

      tape->capabilities = *capabilities;       /* Save us a copy */
      if (capabilities->blk512)
            tape->tape_block_size = 512;
      else if (capabilities->blk1024)
            tape->tape_block_size = 1024;

#if IDETAPE_DEBUG_INFO
      printk(KERN_INFO "ide-tape: Dumping the results of the MODE SENSE packet command\n");
      printk(KERN_INFO "ide-tape: Mode Parameter Header:\n");
      printk(KERN_INFO "ide-tape: Mode Data Length - %d\n",header->mode_data_length);
      printk(KERN_INFO "ide-tape: Medium Type - %d\n",header->medium_type);
      printk(KERN_INFO "ide-tape: Device Specific Parameter - %d\n",header->dsp);
      printk(KERN_INFO "ide-tape: Block Descriptor Length - %d\n",header->bdl);
      
      printk(KERN_INFO "ide-tape: Capabilities and Mechanical Status Page:\n");
      printk(KERN_INFO "ide-tape: Page code - %d\n",capabilities->page_code);
      printk(KERN_INFO "ide-tape: Page length - %d\n",capabilities->page_length);
      printk(KERN_INFO "ide-tape: Read only - %s\n",capabilities->ro ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports reverse space - %s\n",capabilities->sprev ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports erase initiated formatting - %s\n",capabilities->efmt ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports QFA two Partition format - %s\n",capabilities->qfa ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports locking the medium - %s\n",capabilities->lock ? "Yes":"No");
      printk(KERN_INFO "ide-tape: The volume is currently locked - %s\n",capabilities->locked ? "Yes":"No");
      printk(KERN_INFO "ide-tape: The device defaults in the prevent state - %s\n",capabilities->prevent ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports ejecting the medium - %s\n",capabilities->eject ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports error correction - %s\n",capabilities->ecc ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports data compression - %s\n",capabilities->cmprs ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports 512 bytes block size - %s\n",capabilities->blk512 ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports 1024 bytes block size - %s\n",capabilities->blk1024 ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Supports 32768 bytes block size / Restricted byte count for PIO transfers - %s\n",capabilities->blk32768 ? "Yes":"No");
      printk(KERN_INFO "ide-tape: Maximum supported speed in KBps - %d\n",capabilities->max_speed);
      printk(KERN_INFO "ide-tape: Continuous transfer limits in blocks - %d\n",capabilities->ctl);
      printk(KERN_INFO "ide-tape: Current speed in KBps - %d\n",capabilities->speed);     
      printk(KERN_INFO "ide-tape: Buffer size - %d\n",capabilities->buffer_size*512);
#endif /* IDETAPE_DEBUG_INFO */
}

/*
 *    ide_get_blocksize_from_block_descriptor does a mode sense page 0 with block descriptor
 *    and if it succeeds sets the tape block size with the reported value
 */
static void idetape_get_blocksize_from_block_descriptor(ide_drive_t *drive)
{

      idetape_tape_t *tape = drive->driver_data;
      idetape_pc_t pc;
      idetape_mode_parameter_header_t *header;
      idetape_parameter_block_descriptor_t *block_descrp;
      
      idetape_create_mode_sense_cmd(&pc, IDETAPE_BLOCK_DESCRIPTOR);
      if (idetape_queue_pc_tail(drive, &pc)) {
            printk(KERN_ERR "ide-tape: Can't get block descriptor\n");
            if (tape->tape_block_size == 0) {
                  printk(KERN_WARNING "ide-tape: Cannot deal with zero block size, assume 32k\n");
                  tape->tape_block_size =  32768;
            }
            return;
      }
      header = (idetape_mode_parameter_header_t *) pc.buffer;
      block_descrp = (idetape_parameter_block_descriptor_t *) (pc.buffer + sizeof(idetape_mode_parameter_header_t));
      tape->tape_block_size =( block_descrp->length[0]<<16) + (block_descrp->length[1]<<8) + block_descrp->length[2];
      tape->drv_write_prot = (header->dsp & 0x80) >> 7;

#if IDETAPE_DEBUG_INFO
      printk(KERN_INFO "ide-tape: Adjusted block size - %d\n", tape->tape_block_size);
#endif /* IDETAPE_DEBUG_INFO */
}
static void idetape_add_settings (ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

/*
 *                drive setting name      read/write  ioctl ioctl       data type   min               max               mul_factor              div_factor              data pointer                        set function
 */
      ide_add_setting(drive,  "buffer",   SETTING_READ,     -1,   -1,         TYPE_SHORT, 0,                0xffff,                 1,                      2,                      &tape->capabilities.buffer_size,    NULL);
      ide_add_setting(drive,  "pipeline_min",   SETTING_RW, -1,   -1,         TYPE_INT,   1,                0xffff,                 tape->stage_size / 1024,      1,                      &tape->min_pipeline,                NULL);
      ide_add_setting(drive,  "pipeline", SETTING_RW, -1,   -1,         TYPE_INT,   1,                0xffff,                 tape->stage_size / 1024,      1,                      &tape->max_stages,                  NULL);
      ide_add_setting(drive,  "pipeline_max",   SETTING_RW, -1,   -1,         TYPE_INT,   1,                0xffff,                 tape->stage_size / 1024,      1,                      &tape->max_pipeline,                NULL);
      ide_add_setting(drive,  "pipeline_used",SETTING_READ, -1,   -1,         TYPE_INT,   0,                0xffff,                 tape->stage_size / 1024,      1,                      &tape->nr_stages,             NULL);
      ide_add_setting(drive,  "pipeline_pending",SETTING_READ,-1, -1,         TYPE_INT,   0,                0xffff,                 tape->stage_size / 1024,      1,                      &tape->nr_pending_stages,           NULL);
      ide_add_setting(drive,  "speed",    SETTING_READ,     -1,   -1,         TYPE_SHORT, 0,                0xffff,                 1,                      1,                      &tape->capabilities.speed,          NULL);
      ide_add_setting(drive,  "stage",    SETTING_READ,     -1,   -1,         TYPE_INT,   0,                0xffff,                 1,                      1024,                   &tape->stage_size,                  NULL);
      ide_add_setting(drive,  "tdsc",           SETTING_RW, -1,   -1,         TYPE_INT,   IDETAPE_DSC_RW_MIN,     IDETAPE_DSC_RW_MAX,     1000,                   HZ,                     &tape->best_dsc_rw_frequency,       NULL);
      ide_add_setting(drive,  "dsc_overlap",    SETTING_RW, -1,   -1,         TYPE_BYTE,  0,                1,                1,                      1,                      &drive->dsc_overlap,                NULL);
      ide_add_setting(drive,  "pipeline_head_speed_c",SETTING_READ,     -1,   -1,   TYPE_INT,   0,                0xffff,                 1,                      1,                      &tape->controlled_pipeline_head_speed,    NULL);
      ide_add_setting(drive,  "pipeline_head_speed_u",SETTING_READ,     -1,   -1,   TYPE_INT,   0,                0xffff,                 1,                      1,                      &tape->uncontrolled_pipeline_head_speed,  NULL);
      ide_add_setting(drive,  "avg_speed",      SETTING_READ,     -1,   -1,         TYPE_INT,   0,                0xffff,                 1,                      1,                      &tape->avg_speed,       NULL);
      ide_add_setting(drive,  "debug_level",SETTING_RW,     -1,   -1,         TYPE_INT,   0,                0xffff,                 1,                      1,                      &tape->debug_level,           NULL);
}

/*
 *    ide_setup is called to:
 *
 *          1.    Initialize our various state variables.
 *          2.    Ask the tape for its capabilities.
 *          3.    Allocate a buffer which will be used for data
 *                transfer. The buffer size is chosen based on
 *                the recommendation which we received in step (2).
 *
 *    Note that at this point ide.c already assigned us an irq, so that
 *    we can queue requests here and wait for their completion.
 */
static void idetape_setup (ide_drive_t *drive, idetape_tape_t *tape, int minor)
{
      unsigned long t1, tmid, tn, t;
      int speed;
      struct idetape_id_gcw gcw;
      int stage_size;
      struct sysinfo si;

      spin_lock_init(&tape->spinlock);
      drive->dsc_overlap = 1;
#ifdef CONFIG_BLK_DEV_IDEPCI
      if (HWIF(drive)->pci_dev != NULL) {
            /*
             * These two ide-pci host adapters appear to need DSC overlap disabled.
             * This probably needs further analysis.
             */
            if ((HWIF(drive)->pci_dev->device == PCI_DEVICE_ID_ARTOP_ATP850UF) ||
                (HWIF(drive)->pci_dev->device == PCI_DEVICE_ID_TTI_HPT343)) {
                  printk(KERN_INFO "ide-tape: %s: disabling DSC overlap\n", tape->name);
                  drive->dsc_overlap = 0;
            }
      }
#endif /* CONFIG_BLK_DEV_IDEPCI */
      /* Seagate Travan drives do not support DSC overlap. */
      if (strstr(drive->id->model, "Seagate STT3401"))
            drive->dsc_overlap = 0;
      tape->minor = minor;
      tape->name[0] = 'h';
      tape->name[1] = 't';
      tape->name[2] = '0' + minor;
      tape->chrdev_direction = idetape_direction_none;
      tape->pc = tape->pc_stack;
      tape->max_insert_speed = 10000;
      tape->speed_control = 1;
      *((unsigned short *) &gcw) = drive->id->config;
      if (gcw.drq_type == 1)
            set_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags);

      tape->min_pipeline = tape->max_pipeline = tape->max_stages = 10;
      
      idetape_get_inquiry_results(drive);
      idetape_get_mode_sense_results(drive);
      idetape_get_blocksize_from_block_descriptor(drive);
      tape->user_bs_factor = 1;
      tape->stage_size = tape->capabilities.ctl * tape->tape_block_size;
      while (tape->stage_size > 0xffff) {
            printk(KERN_NOTICE "ide-tape: decreasing stage size\n");
            tape->capabilities.ctl /= 2;
            tape->stage_size = tape->capabilities.ctl * tape->tape_block_size;
      }
      stage_size = tape->stage_size;
      tape->pages_per_stage = stage_size / PAGE_SIZE;
      if (stage_size % PAGE_SIZE) {
            tape->pages_per_stage++;
            tape->excess_bh_size = PAGE_SIZE - stage_size % PAGE_SIZE;
      }

      /*
       *    Select the "best" DSC read/write polling frequency
       *    and pipeline size.
       */
      speed = max(tape->capabilities.speed, tape->capabilities.max_speed);

      tape->max_stages = speed * 1000 * 10 / tape->stage_size;

      /*
       *    Limit memory use for pipeline to 10% of physical memory
       */
      si_meminfo(&si);
      if (tape->max_stages * tape->stage_size > si.totalram * si.mem_unit / 10)
            tape->max_stages = si.totalram * si.mem_unit / (10 * tape->stage_size);
      tape->max_stages   = min(tape->max_stages, IDETAPE_MAX_PIPELINE_STAGES);
      tape->min_pipeline = min(tape->max_stages, IDETAPE_MIN_PIPELINE_STAGES);
      tape->max_pipeline = min(tape->max_stages * 2, IDETAPE_MAX_PIPELINE_STAGES);
      if (tape->max_stages == 0)
            tape->max_stages = tape->min_pipeline = tape->max_pipeline = 1;

      t1 = (tape->stage_size * HZ) / (speed * 1000);
      tmid = (tape->capabilities.buffer_size * 32 * HZ) / (speed * 125);
      tn = (IDETAPE_FIFO_THRESHOLD * tape->stage_size * HZ) / (speed * 1000);

      if (tape->max_stages)
            t = tn;
      else
            t = t1;

      /*
       *    Ensure that the number we got makes sense; limit
       *    it within IDETAPE_DSC_RW_MIN and IDETAPE_DSC_RW_MAX.
       */
      tape->best_dsc_rw_frequency = max_t(unsigned long, min_t(unsigned long, t, IDETAPE_DSC_RW_MAX), IDETAPE_DSC_RW_MIN);
      printk(KERN_INFO "ide-tape: %s <-> %s: %dKBps, %d*%dkB buffer, "
            "%dkB pipeline, %lums tDSC%s\n",
            drive->name, tape->name, tape->capabilities.speed,
            (tape->capabilities.buffer_size * 512) / tape->stage_size,
            tape->stage_size / 1024,
            tape->max_stages * tape->stage_size / 1024,
            tape->best_dsc_rw_frequency * 1000 / HZ,
            drive->using_dma ? ", DMA":"");

      idetape_add_settings(drive);
}

static void ide_tape_remove(ide_drive_t *drive)
{
      idetape_tape_t *tape = drive->driver_data;

      ide_unregister_subdriver(drive, tape->driver);

      ide_unregister_region(tape->disk);

      ide_tape_put(tape);
}

static void ide_tape_release(struct kref *kref)
{
      struct ide_tape_obj *tape = to_ide_tape(kref);
      ide_drive_t *drive = tape->drive;
      struct gendisk *g = tape->disk;

      BUG_ON(tape->first_stage != NULL || tape->merge_stage_size);

      drive->dsc_overlap = 0;
      drive->driver_data = NULL;
      class_device_destroy(idetape_sysfs_class,
                  MKDEV(IDETAPE_MAJOR, tape->minor));
      class_device_destroy(idetape_sysfs_class,
                  MKDEV(IDETAPE_MAJOR, tape->minor + 128));
      idetape_devs[tape->minor] = NULL;
      g->private_data = NULL;
      put_disk(g);
      kfree(tape);
}

#ifdef CONFIG_PROC_FS

static int proc_idetape_read_name
      (char *page, char **start, off_t off, int count, int *eof, void *data)
{
      ide_drive_t *drive = (ide_drive_t *) data;
      idetape_tape_t    *tape = drive->driver_data;
      char        *out = page;
      int         len;

      len = sprintf(out, "%s\n", tape->name);
      PROC_IDE_READ_RETURN(page, start, off, count, eof, len);
}

static ide_proc_entry_t idetape_proc[] = {
      { "capacity",     S_IFREG|S_IRUGO,  proc_ide_read_capacity, NULL },
      { "name",   S_IFREG|S_IRUGO,  proc_idetape_read_name, NULL },
      { NULL, 0, NULL, NULL }
};

#else

#define     idetape_proc      NULL

#endif

static int ide_tape_probe(ide_drive_t *);

static ide_driver_t idetape_driver = {
      .gen_driver = {
            .owner            = THIS_MODULE,
            .name       = "ide-tape",
            .bus        = &ide_bus_type,
      },
      .probe                  = ide_tape_probe,
      .remove                 = ide_tape_remove,
      .version          = IDETAPE_VERSION,
      .media                  = ide_tape,
      .supports_dsc_overlap   = 1,
      .do_request       = idetape_do_request,
      .end_request            = idetape_end_request,
      .error                  = __ide_error,
      .abort                  = __ide_abort,
      .proc             = idetape_proc,
};

/*
 *    Our character device supporting functions, passed to register_chrdev.
 */
static struct file_operations idetape_fops = {
      .owner            = THIS_MODULE,
      .read       = idetape_chrdev_read,
      .write            = idetape_chrdev_write,
      .ioctl            = idetape_chrdev_ioctl,
      .open       = idetape_chrdev_open,
      .release    = idetape_chrdev_release,
};

static int idetape_open(struct inode *inode, struct file *filp)
{
      struct gendisk *disk = inode->i_bdev->bd_disk;
      struct ide_tape_obj *tape;
      ide_drive_t *drive;

      if (!(tape = ide_tape_get(disk)))
            return -ENXIO;

      drive = tape->drive;

      drive->usage++;

      return 0;
}

static int idetape_release(struct inode *inode, struct file *filp)
{
      struct gendisk *disk = inode->i_bdev->bd_disk;
      struct ide_tape_obj *tape = ide_tape_g(disk);
      ide_drive_t *drive = tape->drive;

      drive->usage--;

      ide_tape_put(tape);

      return 0;
}

static int idetape_ioctl(struct inode *inode, struct file *file,
                  unsigned int cmd, unsigned long arg)
{
      struct block_device *bdev = inode->i_bdev;
      struct ide_tape_obj *tape = ide_tape_g(bdev->bd_disk);
      ide_drive_t *drive = tape->drive;
      int err = generic_ide_ioctl(drive, file, bdev, cmd, arg);
      if (err == -EINVAL)
            err = idetape_blkdev_ioctl(drive, cmd, arg);
      return err;
}

static struct block_device_operations idetape_block_ops = {
      .owner            = THIS_MODULE,
      .open       = idetape_open,
      .release    = idetape_release,
      .ioctl            = idetape_ioctl,
};

static int ide_tape_probe(ide_drive_t *drive)
{
      idetape_tape_t *tape;
      struct gendisk *g;
      int minor;

      if (!strstr("ide-tape", drive->driver_req))
            goto failed;
      if (!drive->present)
            goto failed;
      if (drive->media != ide_tape)
            goto failed;
      if (!idetape_identify_device (drive)) {
            printk(KERN_ERR "ide-tape: %s: not supported by this version of ide-tape\n", drive->name);
            goto failed;
      }
      if (drive->scsi) {
            printk("ide-tape: passing drive %s to ide-scsi emulation.\n", drive->name);
            goto failed;
      }
      if (strstr(drive->id->model, "OnStream DI-")) {
            printk(KERN_WARNING "ide-tape: Use drive %s with ide-scsi emulation and osst.\n", drive->name);
            printk(KERN_WARNING "ide-tape: OnStream support will be removed soon from ide-tape!\n");
      }
      tape = (idetape_tape_t *) kzalloc (sizeof (idetape_tape_t), GFP_KERNEL);
      if (tape == NULL) {
            printk(KERN_ERR "ide-tape: %s: Can't allocate a tape structure\n", drive->name);
            goto failed;
      }

      g = alloc_disk(1 << PARTN_BITS);
      if (!g)
            goto out_free_tape;

      ide_init_disk(g, drive);

      ide_register_subdriver(drive, &idetape_driver);

      kref_init(&tape->kref);

      tape->drive = drive;
      tape->driver = &idetape_driver;
      tape->disk = g;

      g->private_data = &tape->driver;

      drive->driver_data = tape;

      mutex_lock(&idetape_ref_mutex);
      for (minor = 0; idetape_devs[minor]; minor++)
            ;
      idetape_devs[minor] = tape;
      mutex_unlock(&idetape_ref_mutex);

      idetape_setup(drive, tape, minor);

      class_device_create(idetape_sysfs_class, NULL,
                  MKDEV(IDETAPE_MAJOR, minor), &drive->gendev, "%s", tape->name);
      class_device_create(idetape_sysfs_class, NULL,
                  MKDEV(IDETAPE_MAJOR, minor + 128), &drive->gendev, "n%s", tape->name);

      g->fops = &idetape_block_ops;
      ide_register_region(g);

      return 0;

out_free_tape:
      kfree(tape);
failed:
      return -ENODEV;
}

MODULE_DESCRIPTION("ATAPI Streaming TAPE Driver");
MODULE_LICENSE("GPL");

static void __exit idetape_exit (void)
{
      driver_unregister(&idetape_driver.gen_driver);
      class_destroy(idetape_sysfs_class);
      unregister_chrdev(IDETAPE_MAJOR, "ht");
}

static int __init idetape_init(void)
{
      int error = 1;
      idetape_sysfs_class = class_create(THIS_MODULE, "ide_tape");
      if (IS_ERR(idetape_sysfs_class)) {
            idetape_sysfs_class = NULL;
            printk(KERN_ERR "Unable to create sysfs class for ide tapes\n");
            error = -EBUSY;
            goto out;
      }

      if (register_chrdev(IDETAPE_MAJOR, "ht", &idetape_fops)) {
            printk(KERN_ERR "ide-tape: Failed to register character device interface\n");
            error = -EBUSY;
            goto out_free_class;
      }

      error = driver_register(&idetape_driver.gen_driver);
      if (error)
            goto out_free_driver;

      return 0;

out_free_driver:
      driver_unregister(&idetape_driver.gen_driver);
out_free_class:
      class_destroy(idetape_sysfs_class);
out:
      return error;
}

MODULE_ALIAS("ide:*m-tape*");
module_init(idetape_init);
module_exit(idetape_exit);
MODULE_ALIAS_CHARDEV_MAJOR(IDETAPE_MAJOR);

Generated by  Doxygen 1.6.0   Back to index