Import 2.3.9pre5

[davej-history.git] / drivers / block / ide-tape.c

/*
 * linux/drivers/block/ide-tape.c       Version 1.14            Dec  30, 1998
 *
 * Copyright (C) 1995 - 1998 Gadi Oxman <gadio@netvision.net.il>
 *
 * 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.
 *
 * 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 "1.13"

#include <linux/config.h>
#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/major.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/malloc.h>
#include <linux/pci.h>
#include <linux/ide.h>

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

/*
 *      For general magnetic tape device compatibility.
 */
#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 will disable the pipelined mode.
 */
#define IDETAPE_MIN_PIPELINE_STAGES     100
#define IDETAPE_MAX_PIPELINE_STAGES     200
#define IDETAPE_INCREASE_STAGES_RATE     20

/*
 *      Assuming the tape shares an interface with another device, the default
 *      behavior is to service our pending pipeline requests as soon as
 *      possible, but to gracefully postpone them in favor of the other device
 *      when the tape is busy. This has the potential to maximize our
 *      throughput and in the same time, to make efficient use of the IDE bus.
 *
 *      Note that when we transfer data to / from the tape, we co-operate with
 *      the relatively fast tape buffers and the tape will perform the
 *      actual media access in the background, without blocking the IDE
 *      bus. This means that as long as the maximum IDE bus throughput is much
 *      higher than the sum of our maximum throughput and the maximum
 *      throughput of the other device, we should probably leave the default
 *      behavior.
 *
 *      However, if it is still desired to give the other device a share even
 *      in our own (small) bus bandwidth, you can set IDETAPE_LOW_TAPE_PRIORITY
 *      to 1. This will let the other device finish *all* its pending requests
 *      before we even check if we can service our next pending request.
 */
#define IDETAPE_LOW_TAPE_PRIORITY       0

/*
 *      The following are used to debug the driver:
 *
 *      Setting IDETAPE_INFO_LOG to 1 will log driver vender information.
 *      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_INFO_LOG                0
#define IDETAPE_DEBUG_LOG               0
#define IDETAPE_DEBUG_BUGS              1

#if IDETAPE_DEBUG_LOG
#undef IDETAPE_INFO_LOG
#define IDETAPE_INFO_LOG                IDETAPE_DEBUG_LOG
#endif

/*
 *      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)

/*
 *      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.
 */
 
/*
 *      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

/*
 *      Some tape drives require a long irq timeout
 */
#define IDETAPE_WAIT_CMD                (60*HZ)

/*
 *      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 ***********************/

typedef enum {
        idetape_direction_none,
        idetape_direction_read,
        idetape_direction_write
} idetape_chrdev_direction_t;

/*
 *      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 buffer_head *bh;
        char *b_data;
        int b_count;
        byte *buffer;                           /* Data buffer */
        byte *current_position;                 /* Pointer into the above buffer */
        void (*callback) (ide_drive_t *);       /* Called when this packet command is completed */
        byte pc_buffer[IDETAPE_PC_BUFFER_SIZE]; /* Temporary buffer */
        unsigned int flags;                     /* Status/Action bit flags */
} idetape_pc_t;

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

/*
 *      Capabilities and Mechanical Status Page
 */
typedef struct {
        unsigned        page_code       :6;     /* Page code - Should be 0x2a */
        unsigned        reserved1_67    :2;
        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 */
        unsigned        reserved6_45    :2;     /* Reserved */  
        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        slowb           :1;     /* The device restricts the byte count for PIO */
                                                /* transfers for slow buffer memory ??? */
        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;

/*
 *      A pipeline stage.
 */
typedef struct idetape_stage_s {
        struct request rq;                      /* The corresponding request */
        struct buffer_head *bh;                 /* The data buffers */
        struct idetape_stage_s *next;           /* Pointer to the next stage */
} idetape_stage_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_drive_t *drive;

        /*
         *      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.
         */
        idetape_pc_t *pc;                       /* Current packet command */
        idetape_pc_t *failed_pc;                /* Last failed packet command */
        idetape_pc_t pc_stack[IDETAPE_PC_STACK];/* Packet command stack */
        int pc_stack_index;                     /* Next free packet command storage space */
        struct request rq_stack[IDETAPE_PC_STACK];
        int rq_stack_index;                     /* We implement a circular array */

        /*
         *      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;
        unsigned long dsc_polling_start;        /* The time in which we started polling for DSC */
        struct timer_list dsc_timer;            /* Timer used to poll for dsc */
        unsigned long best_dsc_rw_frequency;    /* Read/Write dsc polling frequency */
        unsigned long dsc_polling_frequency;    /* The current polling frequency */
        unsigned long dsc_timeout;              /* Maximum waiting time */

        /*
         *      Position information
         */
        byte partition;
        unsigned int block_address;             /* Current block */

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

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

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

        /*
         *      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.
         */
        struct request *active_data_request;    /* Pointer to the request which is waiting in the device request queue */
        int stage_size;                         /* Data buffer size (chosen based on the tape's recommendation */
        idetape_stage_t *merge_stage;
        int merge_stage_size;
        struct buffer_head *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).
         */
        int nr_stages;                          /* Number of currently used stages */
        int nr_pending_stages;                  /* Number of pending stages */
        int max_stages, min_pipeline, max_pipeline; /* We will not allocate more than this number of stages */
        idetape_stage_t *first_stage;           /* The first stage which will be removed from the pipeline */
        idetape_stage_t *active_stage;          /* The currently active stage */
        idetape_stage_t *next_stage;            /* Will be serviced after the currently active request */
        idetape_stage_t *last_stage;            /* New requests will be added to the pipeline here */
        idetape_stage_t *cache_stage;           /* Optional free stage which we can use */
        int pages_per_stage;
        int excess_bh_size;                     /* Wasted space in each stage */

        unsigned int flags;                     /* Status/Action flags */
} idetape_tape_t;

/*
 *      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 */

/*
 *      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_LOAD_UNLOAD_CMD         0x1b
#define IDETAPE_LOCATE_CMD              0x2b
#define IDETAPE_READ_POSITION_CMD       0x34

/*
 *      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.
 *
 */
#define IDETAPE_FIRST_RQ                90

/*
 *      IDETAPE_PC_RQ is used to queue a packet command in the request queue.
 */
#define IDETAPE_PC_RQ1                  90
#define IDETAPE_PC_RQ2                  91

/*
 *      IDETAPE_READ_RQ and IDETAPE_WRITE_RQ are used by our
 *      character device interface to request read/write operations from
 *      our block device interface.
 */
#define IDETAPE_READ_RQ                 92
#define IDETAPE_WRITE_RQ                93
#define IDETAPE_ABORTED_WRITE_RQ        94

#define IDETAPE_LAST_RQ                 94

/*
 *      A macro which can be used to check if a we support a given
 *      request command.
 */
#define IDETAPE_RQ_CMD(cmd)             ((cmd >= IDETAPE_FIRST_RQ) && (cmd <= IDETAPE_LAST_RQ))

/*
 *      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 ATAPI Status Register.
 */
typedef union {
        unsigned all                    :8;
        struct {
                unsigned check          :1;     /* Error occurred */
                unsigned idx            :1;     /* Reserved */
                unsigned corr           :1;     /* Correctable error occurred */
                unsigned drq            :1;     /* Data is request by the device */
                unsigned dsc            :1;     /* Buffer availability / Media access command finished */
                unsigned reserved5      :1;     /* Reserved */
                unsigned drdy           :1;     /* Ignored for ATAPI commands (ready to accept ATA command) */
                unsigned bsy            :1;     /* The device has access to the command block */
        } b;
} idetape_status_reg_t;

/*
 *      The ATAPI error register.
 */
typedef union {
        unsigned all                    :8;
        struct {
                unsigned ili            :1;     /* Illegal Length Indication */
                unsigned eom            :1;     /* End Of Media Detected */
                unsigned abrt           :1;     /* Aborted command - As defined by ATA */
                unsigned mcr            :1;     /* Media Change Requested - As defined by ATA */
                unsigned sense_key      :4;     /* Sense key of the last failed packet command */
        } b;
} idetape_error_reg_t;

/*
 *      ATAPI Feature Register
 */
typedef union {
        unsigned all                    :8;
        struct {
                unsigned dma            :1;     /* Using DMA of PIO */
                unsigned reserved321    :3;     /* Reserved */
                unsigned reserved654    :3;     /* Reserved (Tag Type) */
                unsigned reserved7      :1;     /* Reserved */
        } b;
} idetape_feature_reg_t;

/*
 *      ATAPI Byte Count Register.
 */
typedef union {
        unsigned all                    :16;
        struct {
                unsigned low            :8;     /* LSB */
                unsigned high           :8;     /* MSB */
        } b;
} idetape_bcount_reg_t;

/*
 *      ATAPI Interrupt Reason Register.
 */
typedef union {
        unsigned all                    :8;
        struct {
                unsigned cod            :1;     /* Information transferred is command (1) or data (0) */
                unsigned io             :1;     /* The device requests us to read (1) or write (0) */
                unsigned reserved       :6;     /* Reserved */
        } b;
} idetape_ireason_reg_t;

/*
 *      ATAPI Drive Select Register
 */
typedef union { 
        unsigned all                    :8;
        struct {
                unsigned sam_lun        :4;     /* Should be zero with ATAPI (not used) */
                unsigned drv            :1;     /* The responding drive will be drive 0 (0) or drive 1 (1) */
                unsigned one5           :1;     /* Should be set to 1 */
                unsigned reserved6      :1;     /* Reserved */
                unsigned one7           :1;     /* Should be set to 1 */
        } b;
} idetape_drivesel_reg_t;

/*
 *      ATAPI Device Control Register
 */
typedef union {                 
        unsigned all                    :8;
        struct {
                unsigned zero0          :1;     /* Should be set to zero */
                unsigned nien           :1;     /* Device interrupt is disabled (1) or enabled (0) */
                unsigned srst           :1;     /* ATA software reset. ATAPI devices should use the new ATAPI srst. */
                unsigned one3           :1;     /* Should be set to 1 */
                unsigned reserved4567   :4;     /* Reserved */
        } b;
} idetape_control_reg_t;

/*
 *      idetape_chrdev_t provides the link between out character device
 *      interface and our block device interface and the corresponding
 *      ide_drive_t structure.
 */
typedef struct {
        ide_drive_t *drive;
} idetape_chrdev_t;

/*
 *      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;

/*
 *      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;

/*
 *      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_CAPABILITIES_PAGE       0x2a

/*
 *      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 */
} 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 idetape_chrdev_t idetape_chrdevs[MAX_HWIFS * MAX_DRIVES];
static int idetape_chrdev_present = 0;

/*
 *      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--)
                IN_BYTE (IDE_DATA_REG);
}

static void idetape_input_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
        struct buffer_head *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 = IDE_MIN (bh->b_size - bh->b_count, bcount);
                atapi_input_bytes (drive, bh->b_data + bh->b_count, count);
                bcount -= count; bh->b_count += count;
                if (bh->b_count == bh->b_size) {
                        bh = bh->b_reqnext;
                        if (bh)
                                bh->b_count = 0;
                }
        }
        pc->bh = bh;
}

static void idetape_output_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
        struct buffer_head *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 = IDE_MIN (pc->b_count, bcount);
                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 = bh->b_count;
                        }
                }
        }
}

#ifdef CONFIG_BLK_DEV_IDEDMA
static void idetape_update_buffers (idetape_pc_t *pc)
{
        struct buffer_head *bh = pc->bh;
        int count, 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 = IDE_MIN (bh->b_size, bcount);
                bh->b_count = count;
                if (bh->b_count == bh->b_size)
                        bh = bh->b_reqnext;
                bcount -= count;
        }
        pc->bh = bh;
}
#endif /* CONFIG_BLK_DEV_IDEDMA */

/*
 *      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;

        tape->postponed_rq = HWGROUP(drive)->rq;
        ide_stall_queue(drive, tape->dsc_polling_frequency);
}

/*
 *      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)
{
        ide_init_drive_cmd (rq);
        rq->buffer = (char *) pc;
        rq->cmd = IDETAPE_PC_RQ1;
        (void) ide_do_drive_cmd (drive, rq, ide_preempt);
}

/*
 *      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
        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
        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++]);
}

/*
 *      Pipeline related functions
 */

static inline int idetape_pipeline_active (idetape_tape_t *tape)
{
        return tape->active_data_request != NULL;
}

/*
 *      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 buffer_head *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)
{
        if (tape->cache_stage == NULL)
                tape->cache_stage = stage;
        else
                __idetape_kfree_stage (stage);
}

/*
 *      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)
{
        idetape_stage_t *stage;
        struct buffer_head *prev_bh, *bh;
        int pages = tape->pages_per_stage;
        char *b_data;

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

        bh = stage->bh = (struct buffer_head *) kmalloc (sizeof (struct buffer_head), GFP_KERNEL);
        if (bh == NULL)
                goto abort;
        bh->b_reqnext = NULL;
        if ((bh->b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
                goto abort;
        bh->b_size = PAGE_SIZE;
        set_bit (BH_Lock, &bh->b_state);

        while (--pages) {
                if ((b_data = (char *) __get_free_page (GFP_KERNEL)) == NULL)
                        goto abort;
                if (bh->b_data == b_data + PAGE_SIZE && virt_to_bus (bh->b_data) == virt_to_bus (b_data) + PAGE_SIZE) {
                        bh->b_size += PAGE_SIZE;
                        bh->b_data -= PAGE_SIZE;
                        continue;
                }
                if (b_data == bh->b_data + bh->b_size && virt_to_bus (b_data) == virt_to_bus (bh->b_data) + bh->b_size) {
                        bh->b_size += PAGE_SIZE;
                        continue;
                }
                prev_bh = bh;
                if ((bh = (struct buffer_head *) kmalloc (sizeof (struct buffer_head), 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;
                set_bit (BH_Lock, &bh->b_state);
                prev_bh->b_reqnext = bh;
        }
        bh->b_size -= tape->excess_bh_size;
        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
        printk (KERN_INFO "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);
}

static void idetape_copy_stage_from_user (idetape_tape_t *tape, idetape_stage_t *stage, const char *buf, int n)
{
        struct buffer_head *bh = tape->bh;
        int count;

        while (n) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk (KERN_ERR "ide-tape: bh == NULL in idetape_copy_stage_from_user\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = IDE_MIN (bh->b_size - bh->b_count, n);
                copy_from_user (bh->b_data + bh->b_count, buf, count);
                n -= count; bh->b_count += count; buf += count;
                if (bh->b_count == bh->b_size) {
                        bh = bh->b_reqnext;
                        if (bh)
                                bh->b_count = 0;
                }
        }
        tape->bh = bh;
}

static void idetape_copy_stage_to_user (idetape_tape_t *tape, char *buf, idetape_stage_t *stage, int n)
{
        struct buffer_head *bh = tape->bh;
        int count;

        while (n) {
#if IDETAPE_DEBUG_BUGS
                if (bh == NULL) {
                        printk (KERN_ERR "ide-tape: bh == NULL in idetape_copy_stage_to_user\n");
                        return;
                }
#endif /* IDETAPE_DEBUG_BUGS */
                count = IDE_MIN (tape->b_count, n);
                copy_to_user (buf, tape->b_data, count);
                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 = bh->b_count;
                        }
                }
        }
}

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

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

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

/*
 *      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
        printk (KERN_INFO "Reached idetape_increase_max_pipeline_stages\n");
#endif /* IDETAPE_DEBUG_LOG */

        tape->max_stages += increase;
        tape->max_stages = IDE_MAX(tape->max_stages, tape->min_pipeline);
        tape->max_stages = IDE_MIN(tape->max_stages, tape->max_pipeline);
}

/*
 *      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
        printk (KERN_INFO "Reached idetape_add_stage_tail\n");
#endif /* IDETAPE_DEBUG_LOG */
        spin_lock_irqsave(&HWGROUP(drive)->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(&HWGROUP(drive)->spinlock, flags);
}

/*
 *      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
        printk (KERN_INFO "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 */
        }
}

/*
 *      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
        printk (KERN_INFO "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->buffer = NULL;
        rq->bh = stage->bh;
        tape->active_data_request=rq;
        tape->active_stage=stage;
        tape->next_stage=stage->next;
}

/*
 *      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)) {
                idetape_active_next_stage (drive);
                (void) ide_do_drive_cmd (drive, tape->active_data_request, ide_end);
        }
}

static void idetape_abort_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage = tape->next_stage;

        while (stage) {
                stage->rq.cmd = IDETAPE_ABORTED_WRITE_RQ;
                stage = stage->next;
        }
}

/*
 *      idetape_end_request is used to finish servicing a request, and to
 *      insert a pending pipeline request into the main device queue.
 */
static void idetape_end_request (byte uptodate, ide_hwgroup_t *hwgroup)
{
        ide_drive_t *drive = hwgroup->drive;
        struct request *rq = hwgroup->rq;
        idetape_tape_t *tape = drive->driver_data;
        int error;

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "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;

        if (tape->active_data_request == rq) {          /* The request was a pipelined data transfer request */
                tape->active_stage = NULL;
                tape->active_data_request = NULL;
                tape->nr_pending_stages--;
                if (rq->cmd == IDETAPE_WRITE_RQ) {
                        if (error) {
                                set_bit (IDETAPE_PIPELINE_ERROR, &tape->flags);
                                if (error == IDETAPE_ERROR_EOD)
                                        idetape_abort_pipeline (drive);
                        }
                        idetape_remove_stage_head (drive);
                }
                if (tape->next_stage != NULL) {
                        idetape_active_next_stage (drive);

                        /*
                         *      Insert the next request into the request queue.
                         *      The choice of using ide_next or ide_end is now left to the user.
                         */
#if IDETAPE_LOW_TAPE_PRIORITY
                        (void) ide_do_drive_cmd (drive, tape->active_data_request, ide_end);
#else
                        (void) ide_do_drive_cmd (drive, tape->active_data_request, ide_next);
#endif /* IDETAPE_LOW_TAPE_PRIORITY */
                } else if (!error)
                        idetape_increase_max_pipeline_stages (drive);
        }
        ide_end_drive_cmd (drive, 0, 0);
}

/*
 *      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_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.
         */
        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 */

#ifdef CONFIG_BLK_DEV_IDEDMA

        /*
         *      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);
        }
#endif /* CONFIG_BLK_DEV_IDEDMA */
        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;
        }
}

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

#if IDETAPE_DEBUG_LOG
        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 (1,HWGROUP (drive));
        } else {
                printk (KERN_ERR "Error in REQUEST SENSE itself - Aborting request!\n");
                idetape_end_request (0,HWGROUP (drive));
        }
}

/*
 *      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;
}

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] = 255;
        pc->request_transfer = 18;
        pc->callback = &idetape_request_sense_callback;
}

/*
 *      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 void idetape_retry_pc (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc;
        struct request *rq;
        idetape_error_reg_t error;

        error.all = IN_BYTE (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);
}

/*
 *      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 void idetape_pc_intr (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_status_reg_t status;
        idetape_bcount_reg_t bcount;
        idetape_ireason_reg_t ireason;
        idetape_pc_t *pc=tape->pc;
        unsigned int temp;

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

#ifdef CONFIG_BLK_DEV_IDEDMA
        if (test_bit (PC_DMA_IN_PROGRESS, &pc->flags)) {
                if (HWIF(drive)->dmaproc(ide_dma_end, drive)) {
                        /*
                         * 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).
                         */
                        set_bit (PC_DMA_ERROR, &pc->flags);
                } else {
                        pc->actually_transferred=pc->request_transfer;
                        idetape_update_buffers (pc);
                }
#if IDETAPE_DEBUG_LOG
                printk (KERN_INFO "ide-tape: DMA finished\n");
#endif /* IDETAPE_DEBUG_LOG */
        }
#endif /* CONFIG_BLK_DEV_IDEDMA */

        status.all = GET_STAT();                                        /* Clear the interrupt */

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

                ide__sti();     /* local CPU only */

                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
                        printk (KERN_INFO "ide-tape: %s: I/O error, ",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");
                                ide_do_reset (drive);
                                return;
                        }
                        idetape_retry_pc (drive);                               /* Retry operation */
                        return;
                }
                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;
                        idetape_postpone_request (drive);               /* Allow ide.c to handle other requests */
                        return;
                }
                if (tape->failed_pc == pc)
                        tape->failed_pc=NULL;
                pc->callback(drive);                    /* Command finished - Call the callback function */
                return;
        }
#ifdef CONFIG_BLK_DEV_IDEDMA
        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) HWIF(drive)->dmaproc(ide_dma_off, drive);
                ide_do_reset (drive);
                return;
        }
#endif /* CONFIG_BLK_DEV_IDEDMA */
        bcount.b.high=IN_BYTE (IDE_BCOUNTH_REG);                        /* Get the number of bytes to transfer */
        bcount.b.low=IN_BYTE (IDE_BCOUNTL_REG);                         /* on this interrupt */
        ireason.all=IN_BYTE (IDE_IREASON_REG);

        if (ireason.b.cod) {
                printk (KERN_ERR "ide-tape: CoD != 0 in idetape_pc_intr\n");
                ide_do_reset (drive);
                return;
        }
        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 "but the tape wants us to %s !\n",ireason.b.io ? "Read":"Write");
                ide_do_reset (drive);
                return;
        }
        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);
                                return;
                        }
#if IDETAPE_DEBUG_LOG
                        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
                        atapi_output_bytes (drive,pc->current_position,bcount.all);     /* Write the current buffer */
        } else {
                if (pc->bh != NULL)
                        idetape_input_buffers (drive, pc, bcount.all);
                else
                        atapi_input_bytes (drive,pc->current_position,bcount.all);      /* Read the current buffer */
        }
        pc->actually_transferred+=bcount.all;                                   /* Update the current position */
        pc->current_position+=bcount.all;

        ide_set_handler (drive,&idetape_pc_intr,IDETAPE_WAIT_CMD);              /* And set the interrupt handler again */
}

/*
 *      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 void idetape_transfer_pc(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        idetape_ireason_reg_t ireason;
        int retries = 100;

        if (ide_wait_stat (drive,DRQ_STAT,BUSY_STAT,WAIT_READY)) {
                printk (KERN_ERR "ide-tape: Strange, packet command initiated yet DRQ isn't asserted\n");
                return;
        }
        ireason.all=IN_BYTE (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 = IN_BYTE(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");
                ide_do_reset (drive);
                return;
        }
        ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD);     /* Set the interrupt routine */
        atapi_output_bytes (drive,pc->c,12);                    /* Send the actual packet */
}

static void idetape_issue_packet_command (ide_drive_t *drive, idetape_pc_t *pc)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_bcount_reg_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;
        tape->pc=pc;                                                    /* Set the current packet command */

        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 DMA error in the end of media, for
                 *      example).
                 */
                if (!test_bit (PC_ABORT, &pc->flags)) {
                        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);
                        pc->error = IDETAPE_ERROR_GENERAL;              /* Giving up */
                }
                tape->failed_pc=NULL;
                pc->callback(drive);
                return;
        }
#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Retry number - %d\n",pc->retries);
#endif /* IDETAPE_DEBUG_LOG */

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

#ifdef CONFIG_BLK_DEV_IDEDMA
        if (test_and_clear_bit (PC_DMA_ERROR, &pc->flags)) {
                printk (KERN_WARNING "ide-tape: DMA disabled, reverting to PIO\n");
                (void) HWIF(drive)->dmaproc(ide_dma_off, drive);
        }
        if (test_bit (PC_DMA_RECOMMENDED, &pc->flags) && drive->using_dma)
                dma_ok=!HWIF(drive)->dmaproc(test_bit (PC_WRITING, &pc->flags) ? ide_dma_write : ide_dma_read, drive);
#endif /* CONFIG_BLK_DEV_IDEDMA */

        if (IDE_CONTROL_REG)
                OUT_BYTE (drive->ctl,IDE_CONTROL_REG);
        OUT_BYTE (dma_ok ? 1:0,IDE_FEATURE_REG);                        /* Use PIO/DMA */
        OUT_BYTE (bcount.b.high,IDE_BCOUNTH_REG);
        OUT_BYTE (bcount.b.low,IDE_BCOUNTL_REG);
        OUT_BYTE (drive->select.all,IDE_SELECT_REG);
#ifdef CONFIG_BLK_DEV_IDEDMA
        if (dma_ok) {                                           /* Begin DMA, if necessary */
                set_bit (PC_DMA_IN_PROGRESS, &pc->flags);
                (void) (HWIF(drive)->dmaproc(ide_dma_begin, drive));
        }
#endif /* CONFIG_BLK_DEV_IDEDMA */
        if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
                ide_set_handler(drive, &idetape_transfer_pc, IDETAPE_WAIT_CMD);
                OUT_BYTE(WIN_PACKETCMD, IDE_COMMAND_REG);
        } else {
                OUT_BYTE(WIN_PACKETCMD, IDE_COMMAND_REG);
                idetape_transfer_pc(drive);
        }
}

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

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

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

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

static void 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;

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

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

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

static void idetape_create_locate_cmd (idetape_pc_t *pc, unsigned int block, byte partition)
{
        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 void idetape_create_rewind_cmd (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;
}

/*
 *      A mode sense command is used to "sense" tape parameters.
 */
static void idetape_create_mode_sense_cmd (idetape_pc_t *pc, byte page_code)
{
        idetape_init_pc (pc);
        pc->c[0] = IDETAPE_MODE_SENSE_CMD;
        pc->c[1] = 8;                           /* DBD = 1 - Don't return block descriptors for now */
        pc->c[2] = page_code;
        pc->c[3] = 255;                         /* Don't limit the returned information */
        pc->c[4] = 255;                         /* (We will just discard data in that case) */
        if (page_code == IDETAPE_CAPABILITIES_PAGE)
                pc->request_transfer = 24;
#if IDETAPE_DEBUG_BUGS
        else
                printk (KERN_ERR "ide-tape: unsupported page code in create_mode_sense_cmd\n");
#endif /* IDETAPE_DEBUG_BUGS */
        pc->callback = &idetape_pc_callback;
}

/*
 *      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 (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_load_unload_cmd (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 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_read_cmd (idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct buffer_head *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;
        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_space_cmd (idetape_pc_t *pc,int count,byte 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_create_write_cmd (idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct buffer_head *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 = 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);
}

static void 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
        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
                printk (KERN_INFO "BOP - %s\n",result->bop ? "Yes":"No");
                printk (KERN_INFO "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 (0,HWGROUP (drive));
                } else {
#if IDETAPE_DEBUG_LOG
                        printk (KERN_INFO "Block Location - %lu\n", ntohl (result->first_block));
#endif /* IDETAPE_DEBUG_LOG */
                        tape->partition = result->partition;
                        tape->block_address = ntohl (result->first_block);
                        set_bit (IDETAPE_ADDRESS_VALID, &tape->flags);
                        idetape_end_request (1,HWGROUP (drive));
                }
        } else
                idetape_end_request (0,HWGROUP (drive));
}

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;
}

/*
 *      idetape_do_request is our request handling function.    
 */
static void idetape_do_request (ide_drive_t *drive, struct request *rq, unsigned long block)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc;
        struct request *postponed_rq = tape->postponed_rq;
        idetape_status_reg_t status;

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "rq_status: %d, rq_dev: %u, cmd: %d, errors: %d\n",rq->rq_status,(unsigned int) rq->rq_dev,rq->cmd,rq->errors);
        printk (KERN_INFO "sector: %ld, nr_sectors: %ld, current_nr_sectors: %ld\n",rq->sector,rq->nr_sectors,rq->current_nr_sectors);
#endif /* IDETAPE_DEBUG_LOG */

        if (!IDETAPE_RQ_CMD (rq->cmd)) {
                /*
                 *      We do not support buffer cache originated requests.
                 */
                printk (KERN_NOTICE "ide-tape: %s: Unsupported command in request queue\n", drive->name);
                ide_end_request (0,HWGROUP (drive));                    /* Let the common code handle it */
                return;
        }

        /*
         *      Retry a failed packet command
         */
        if (tape->failed_pc != NULL && tape->pc->c[0] == IDETAPE_REQUEST_SENSE_CMD) {
                idetape_issue_packet_command (drive, tape->failed_pc);
                return;
        }
#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 (0,HWGROUP (drive));
                        return;
                }
#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 = GET_STAT();
        if (!drive->dsc_overlap && rq->cmd != IDETAPE_PC_RQ2)
                set_bit (IDETAPE_IGNORE_DSC, &tape->flags);
        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 ((signed long) (jiffies - tape->dsc_timeout) > 0) {
                        printk (KERN_ERR "ide-tape: %s: DSC timeout\n", tape->name);
                        if (rq->cmd == IDETAPE_PC_RQ2)
                                idetape_media_access_finished (drive);
                        else
                                ide_do_reset (drive);
                        return;
                } else if (jiffies - tape->dsc_polling_start > IDETAPE_DSC_MA_THRESHOLD)
                        tape->dsc_polling_frequency = IDETAPE_DSC_MA_SLOW;
                idetape_postpone_request (drive);
                return;
        }
        switch (rq->cmd) {
                case IDETAPE_READ_RQ:
                        pc=idetape_next_pc_storage (drive);
                        idetape_create_read_cmd (tape, pc, rq->current_nr_sectors, rq->bh);
                        break;
                case IDETAPE_WRITE_RQ:
                        pc=idetape_next_pc_storage (drive);
                        idetape_create_write_cmd (tape, pc, rq->current_nr_sectors, rq->bh);
                        break;
                case IDETAPE_ABORTED_WRITE_RQ:
                        rq->cmd = IDETAPE_WRITE_RQ;
                        rq->errors = IDETAPE_ERROR_EOD;
                        idetape_end_request (1, HWGROUP(drive));
                        return;
                case IDETAPE_PC_RQ1:
                        pc=(idetape_pc_t *) rq->buffer;
                        rq->cmd = IDETAPE_PC_RQ2;
                        break;
                case IDETAPE_PC_RQ2:
                        idetape_media_access_finished (drive);
                        return;
                default:
                        printk (KERN_ERR "ide-tape: bug in IDETAPE_RQ_CMD macro\n");
                        idetape_end_request (0,HWGROUP (drive));
                        return;
        }
        idetape_issue_packet_command (drive, pc);
}

/*
 *      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 request rq;

        ide_init_drive_cmd (&rq);
        rq.buffer = (char *) pc;
        rq.cmd = IDETAPE_PC_RQ1;
        return ide_do_drive_cmd (drive, &rq, ide_wait);
}

/*
 *      idetape_wait_for_request installs a semaphore 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 semaphore (usually by disabling interrupts).
 */
static void idetape_wait_for_request (ide_drive_t *drive, struct request *rq)
{
        DECLARE_MUTEX_LOCKED(sem);

#if IDETAPE_DEBUG_BUGS
        if (rq == NULL || !IDETAPE_RQ_CMD (rq->cmd)) {
                printk (KERN_ERR "ide-tape: bug: Trying to sleep on non-valid request\n");
                return;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        rq->sem = &sem;
        spin_unlock(&HWGROUP(drive)->spinlock);
        down(&sem);
        spin_lock_irq(&HWGROUP(drive)->spinlock);
}

/*
 *      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 buffer_head *bh)
{
        idetape_tape_t *tape = drive->driver_data;
        struct request rq;

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "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 */ 

        ide_init_drive_cmd (&rq);
        rq.bh = bh;
        rq.cmd = cmd;
        rq.sector = tape->block_address;
        rq.nr_sectors = rq.current_nr_sectors = blocks;
        (void) ide_do_drive_cmd (drive, &rq, ide_wait);

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

/*
 *      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;
        idetape_stage_t *new_stage;
        unsigned long flags;
        struct request rq,*rq_ptr;
        int bytes_read;
        
#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_add_chrdev_read_request\n");
#endif /* IDETAPE_DEBUG_LOG */

        ide_init_drive_cmd (&rq);
        rq.cmd = IDETAPE_READ_RQ;
        rq.sector = tape->block_address;
        rq.nr_sectors = rq.current_nr_sectors = blocks;

        if (idetape_pipeline_active (tape) || tape->nr_stages <= tape->max_stages / 4) {
                new_stage=idetape_kmalloc_stage (tape);
                while (new_stage != NULL) {
                        new_stage->rq=rq;
                        idetape_add_stage_tail (drive,new_stage);
                        new_stage=idetape_kmalloc_stage (tape);
                }
                if (!idetape_pipeline_active (tape))
                        idetape_insert_pipeline_into_queue (drive);
        }
        if (tape->first_stage == NULL) {
                /*
                 *      Linux is short on memory. Revert to non-pipelined
                 *      operation mode for this request.
                 */
                return (idetape_queue_rw_tail (drive, IDETAPE_READ_RQ, blocks, tape->merge_stage->bh));
        }
        spin_lock_irqsave(&HWGROUP(drive)->spinlock, flags);
        if (tape->active_stage == tape->first_stage)
                idetape_wait_for_request(drive, tape->active_data_request);
        spin_unlock_irqrestore(&HWGROUP(drive)->spinlock, flags);

        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;

        idetape_switch_buffers (tape, tape->first_stage);

        if (rq_ptr->errors != IDETAPE_ERROR_FILEMARK) {
                clear_bit (IDETAPE_FILEMARK, &tape->flags);
                idetape_remove_stage_head (drive);
        } else
                set_bit (IDETAPE_FILEMARK, &tape->flags);
#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);
}

/*
 *      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
        printk (KERN_INFO "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(&HWGROUP(drive)->spinlock, flags);
                if (idetape_pipeline_active (tape)) {
                        idetape_wait_for_request(drive, tape->active_data_request);
                        spin_unlock_irqrestore(&HWGROUP(drive)->spinlock, flags);
                } else {
                        spin_unlock_irqrestore(&HWGROUP(drive)->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, IDETAPE_WRITE_RQ, blocks, tape->merge_stage->bh);
                }
        }
        rq = &new_stage->rq;
        ide_init_drive_cmd (rq);
        rq->cmd = IDETAPE_WRITE_RQ;
        rq->sector = tape->block_address;       /* Doesn't actually matter - We always assume sequential access */
        rq->nr_sectors = rq->current_nr_sectors = blocks;

        idetape_switch_buffers (tape, new_stage);
        idetape_add_stage_tail (drive,new_stage);

        /*
         *      Check if we are currently servicing requests in the bottom
         *      part of the driver.
         *
         *      If not, wait for the pipeline to be full enough (75%) 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) && tape->nr_stages >= (3 * tape->max_stages) / 4)
                idetape_insert_pipeline_into_queue (drive);

        if (test_and_clear_bit (IDETAPE_PIPELINE_ERROR, &tape->flags))          /* Return a deferred error */
                return -EIO;
        return blocks;
}

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

#if IDETAPE_DEBUG_BUGS
        if (tape->chrdev_direction != idetape_direction_read) {
                printk (KERN_ERR "ide-tape: bug: Trying to discard read pipeline, but we are not reading.\n");
                return;
        }
#endif /* IDETAPE_DEBUG_BUGS */
        tape->merge_stage_size = 0;
        if (tape->merge_stage != NULL) {
                __idetape_kfree_stage (tape->merge_stage);
                tape->merge_stage = NULL;
        }
        tape->chrdev_direction = idetape_direction_none;
        
        if (tape->first_stage == NULL)
                return;

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

        while (tape->first_stage != NULL)
                idetape_remove_stage_head (drive);
        tape->nr_pending_stages = 0;
        tape->max_stages = tape->min_pipeline;
}

/*
 *      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;

        if (!idetape_pipeline_active (tape))
                idetape_insert_pipeline_into_queue (drive);

        spin_lock_irqsave(&HWGROUP(drive)->spinlock, flags);
        if (!idetape_pipeline_active (tape))
                goto abort;
#if IDETAPE_DEBUG_BUGS
        if (tape->last_stage == NULL)
                printk ("ide-tape: tape->last_stage == NULL\n");
        else
#endif /* IDETAPE_DEBUG_BUGS */
        idetape_wait_for_request(drive, &tape->last_stage->rq);
abort:
        spin_unlock_irqrestore(&HWGROUP(drive)->spinlock, flags);
}

static void idetape_pad_zeros (ide_drive_t *drive, int bcount)
{
        idetape_tape_t *tape = drive->driver_data;
        struct buffer_head *bh;
        int count, blocks;
        
        while (bcount) {
                bh = tape->merge_stage->bh;
                count = IDE_MIN (tape->stage_size, bcount);
                bcount -= count;
                blocks = count / tape->tape_block_size;
                while (count) {
                        bh->b_count = IDE_MIN (count, bh->b_size);
                        memset (bh->b_data, 0, bh->b_count);
                        count -= bh->b_count;
                        bh = bh->b_reqnext;
                }
                idetape_queue_rw_tail (drive, IDETAPE_WRITE_RQ, blocks, tape->merge_stage->bh);
        }
}

static void idetape_empty_write_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int blocks, i;
        
#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) {
                        blocks++;
                        i = tape->tape_block_size - tape->merge_stage_size % tape->tape_block_size;
                        memset (tape->bh->b_data + tape->bh->b_count, 0, i);
                        tape->bh->b_count += i;
                }
                (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\n");          
        }
#endif /* IDETAPE_DEBUG_BUGS */
}

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;
}

/*
 *      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, byte partition)
{
        int retval;
        idetape_pc_t pc;

        idetape_create_locate_cmd (&pc, block, partition);
        retval=idetape_queue_pc_tail (drive,&pc);
        if (retval) return (retval);

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

/*
 *      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
        printk (KERN_INFO "Reached idetape_rewind_tape\n");
#endif /* IDETAPE_DEBUG_LOG */  
        
        idetape_create_rewind_cmd (&pc);
        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 int idetape_flush_tape_buffers (ide_drive_t *drive)
{
        idetape_pc_t pc;

        idetape_create_write_filemark_cmd (&pc,0);
        return (idetape_queue_pc_tail (drive,&pc));
}

/*
 *      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, struct inode *inode, struct file *file,
                                 unsigned int cmd, unsigned long arg)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_config_t config;

#if IDETAPE_DEBUG_LOG   
        printk (KERN_INFO "ide-tape: Reached idetape_blkdev_ioctl\n");
#endif /* IDETAPE_DEBUG_LOG */
        switch (cmd) {
                case 0x0340:
                        if (copy_from_user ((char *) &config, (char *) arg, 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 ((char *) arg, (char *) &config, sizeof (idetape_config_t)))
                                return -EFAULT;
                        break;
                default:
                        return -EIO;
        }
        return 0;
}

/*
 *      The block device interface should not be used for data transfers.
 *      However, we still allow opening it so that we can issue general
 *      ide driver configuration ioctl's, such as the interrupt unmask feature.
 */
static int idetape_blkdev_open (struct inode *inode, struct file *filp, ide_drive_t *drive)
{
        MOD_INC_USE_COUNT;
        return 0;
}

static void idetape_blkdev_release (struct inode *inode, struct file *filp, ide_drive_t *drive)
{
        MOD_DEC_USE_COUNT;
}

/*
 *      idetape_pre_reset is called before an ATAPI/ATA software reset.
 */
static void idetape_pre_reset (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        if (tape != NULL)
                set_bit (IDETAPE_IGNORE_DSC, &tape->flags);
}

/*
 *      Character device interface functions
 */
static ide_drive_t *get_drive_ptr (kdev_t i_rdev)
{
        unsigned int i = MINOR(i_rdev) & ~0x80;

        if (i >= MAX_HWIFS * MAX_DRIVES)
                return NULL;
        return (idetape_chrdevs[i].drive);
}

/*
 *      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 (tape->chrdev_direction == idetape_direction_read) {

                /*
                 *      We have a read-ahead buffer. Scan it for crossed
                 *      filemarks.
                 */
                tape->merge_stage_size = 0;
                clear_bit (IDETAPE_FILEMARK, &tape->flags);
                while (tape->first_stage != NULL) {
                        /*
                         *      Wait until the first read-ahead request
                         *      is serviced.
                         */
                        spin_lock_irqsave(&HWGROUP(drive)->spinlock, flags);
                        if (tape->active_stage == tape->first_stage)
                                idetape_wait_for_request(drive, tape->active_data_request);
                        spin_unlock_irqrestore(&HWGROUP(drive)->spinlock, flags);

                        if (tape->first_stage->rq.errors == IDETAPE_ERROR_FILEMARK)
                                count++;
                        if (count == mt_count) {
                                switch (mt_op) {
                                        case MTFSF:
                                                idetape_remove_stage_head (drive);
                                        case MTFSFM:
                                                return (0);
                                        default:
                                                break;
                                }
                        }
                        idetape_remove_stage_head (drive);
                }
                idetape_discard_read_pipeline (drive);
        }

        /*
         *      The filemark was not found in our internal pipeline.
         *      Now we can issue the space command.
         */
        switch (mt_op) {
                case MTFSF:
                        idetape_create_space_cmd (&pc,mt_count-count,IDETAPE_SPACE_OVER_FILEMARK);
                        return (idetape_queue_pc_tail (drive,&pc));
                case MTFSFM:
                        if (!tape->capabilities.sprev)
                                return (-EIO);
                        retval = idetape_space_over_filemarks (drive, MTFSF, mt_count-count);
                        if (retval) return (retval);
                        return (idetape_space_over_filemarks (drive, MTBSF, 1));
                case MTBSF:
                        if (!tape->capabilities.sprev)
                                return (-EIO);
                        idetape_create_space_cmd (&pc,-(mt_count+count),IDETAPE_SPACE_OVER_FILEMARK);
                        return (idetape_queue_pc_tail (drive,&pc));
                case MTBSFM:
                        if (!tape->capabilities.sprev)
                                return (-EIO);
                        retval = idetape_space_over_filemarks (drive, MTBSF, mt_count+count);
                        if (retval) return (retval);
                        return (idetape_space_over_filemarks (drive, MTFSF, 1));
                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).
 *
 *      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.
 */
static ssize_t idetape_chrdev_read (struct file *file, char *buf,
                                    size_t count, loff_t *ppos)
{
        struct inode *inode = file->f_dentry->d_inode;
        ide_drive_t *drive = get_drive_ptr (inode->i_rdev);
        idetape_tape_t *tape = drive->driver_data;
        ssize_t bytes_read,temp,actually_read=0;

        if (ppos != &file->f_pos) {
                /* "A request was outside the capabilities of the device." */
                return -ENXIO;
        }

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_chrdev_read\n");
#endif /* IDETAPE_DEBUG_LOG */
        
        if (tape->chrdev_direction != idetape_direction_read) {         /* Initialize read operation */
                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)) == 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.
                 */
                bytes_read = idetape_queue_rw_tail (drive, IDETAPE_READ_RQ, 0, tape->merge_stage->bh);
                if (bytes_read < 0) {
                        kfree (tape->merge_stage);
                        tape->merge_stage = NULL;
                        tape->chrdev_direction = idetape_direction_none;
                        return bytes_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 (count==0)
                return (0);
        if (tape->merge_stage_size) {
                actually_read=IDE_MIN (tape->merge_stage_size,count);
                idetape_copy_stage_to_user (tape, buf, tape->merge_stage, actually_read);
                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;
                idetape_copy_stage_to_user (tape, buf, tape->merge_stage, bytes_read);
                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=IDE_MIN (count,bytes_read);
                idetape_copy_stage_to_user (tape, buf, tape->merge_stage, temp);
                actually_read+=temp;
                tape->merge_stage_size=bytes_read-temp;
        }
finish:
        if (!actually_read && test_bit (IDETAPE_FILEMARK, &tape->flags))
                idetape_space_over_filemarks (drive, MTFSF, 1);
        return (actually_read);
}
 
static ssize_t idetape_chrdev_write (struct file *file, const char *buf,
                                     size_t count, loff_t *ppos)
{
        struct inode *inode = file->f_dentry->d_inode;
        ide_drive_t *drive = get_drive_ptr (inode->i_rdev);
        idetape_tape_t *tape = drive->driver_data;
        ssize_t retval,actually_written=0;

        if (ppos != &file->f_pos) {
                /* "A request was outside the capabilities of the device." */
                return -ENXIO;
        }

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_chrdev_write\n");
#endif /* IDETAPE_DEBUG_LOG */

        if (tape->chrdev_direction != idetape_direction_write) {        /* Initialize write operation */
                if (tape->chrdev_direction == idetape_direction_read)
                        idetape_discard_read_pipeline (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)) == 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.
                 */
                retval = idetape_queue_rw_tail (drive, IDETAPE_WRITE_RQ, 0, tape->merge_stage->bh);
                if (retval < 0) {
                        kfree (tape->merge_stage);
                        tape->merge_stage = NULL;
                        tape->chrdev_direction = idetape_direction_none;
                        return retval;
                }
                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 (count==0)
                return (0);
        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=IDE_MIN (tape->stage_size-tape->merge_stage_size,count);
                idetape_copy_stage_from_user (tape, tape->merge_stage, buf, actually_written);
                buf+=actually_written;tape->merge_stage_size+=actually_written;count-=actually_written;

                if (tape->merge_stage_size == tape->stage_size) {
                        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) {
                idetape_copy_stage_from_user (tape, tape->merge_stage, buf, tape->stage_size);
                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;
                idetape_copy_stage_from_user (tape, tape->merge_stage, buf, count);
                tape->merge_stage_size+=count;
        }
        return (actually_written);
}

/*
 *      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
 *              supports 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.
 *
 *      The following commands are currently not supported:
 *
 *      MTFSR, MTBSR, 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
        printk (KERN_INFO "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;
        }

        /*
         *      Empty the pipeline.
         */
        if (tape->chrdev_direction == idetape_direction_read)
                idetape_discard_read_pipeline (drive);

        switch (mt_op) {
                case MTWEOF:
                        for (i=0;i<mt_count;i++) {
                                idetape_create_write_filemark_cmd (&pc,1);
                                retval=idetape_queue_pc_tail (drive,&pc);
                                if (retval) return (retval);
                        }
                        return (0);
                case MTREW:
                        return (idetape_rewind_tape (drive));
                case MTLOAD:
                        idetape_create_load_unload_cmd (&pc, IDETAPE_LU_LOAD_MASK);
                        return (idetape_queue_pc_tail (drive,&pc));
                case MTUNLOAD:
                case MTOFFL:
                        idetape_create_load_unload_cmd (&pc,!IDETAPE_LU_LOAD_MASK);
                        return (idetape_queue_pc_tail (drive,&pc));
                case MTNOP:
                        return (idetape_flush_tape_buffers (drive));
                case MTRETEN:
                        idetape_create_load_unload_cmd (&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:
                        return (idetape_position_tape (drive, mt_count * tape->user_bs_factor, tape->partition));
                case MTSETPART:
                        return (idetape_position_tape (drive, 0, mt_count));
                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)
{
        ide_drive_t *drive = get_drive_ptr (inode->i_rdev);
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        struct mtop mtop;
        struct mtget mtget;
        struct mtpos mtpos;
        int retval, block_offset = 0;

#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_chrdev_ioctl, cmd=%u\n",cmd);
#endif /* IDETAPE_DEBUG_LOG */

        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);
                idetape_create_read_position_cmd (&pc);
                retval=idetape_queue_pc_tail (drive,&pc);
                if (retval) return (retval);
        }
        switch (cmd) {
                case MTIOCTOP:
                        if (copy_from_user ((char *) &mtop, (char *) arg, 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_blkno = tape->block_address / 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 (copy_to_user ((char *) arg,(char *) &mtget, sizeof (struct mtget)))
                                return -EFAULT;
                        return 0;
                case MTIOCPOS:
                        mtpos.mt_blkno = tape->block_address / tape->user_bs_factor - block_offset;
                        if (copy_to_user ((char *) arg,(char *) &mtpos, sizeof (struct mtpos)))
                                return -EFAULT;
                        return 0;
                default:
                        if (tape->chrdev_direction == idetape_direction_read)
                                idetape_discard_read_pipeline (drive);
                        return (idetape_blkdev_ioctl (drive,inode,file,cmd,arg));
        }
}

/*
 *      Our character device open function.
 */
static int idetape_chrdev_open (struct inode *inode, struct file *filp)
{
        ide_drive_t *drive;
        idetape_tape_t *tape;
        idetape_pc_t pc;
                        
#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_chrdev_open\n");
#endif /* IDETAPE_DEBUG_LOG */
        
        if ((drive = get_drive_ptr (inode->i_rdev)) == NULL)
                return -ENXIO;
        tape = drive->driver_data;

        if (test_and_set_bit (IDETAPE_BUSY, &tape->flags))
                return -EBUSY;
        MOD_INC_USE_COUNT;
        idetape_create_read_position_cmd (&pc);
        (void) idetape_queue_pc_tail (drive,&pc);
        if (!test_bit (IDETAPE_ADDRESS_VALID, &tape->flags))
                (void) idetape_rewind_tape (drive);
        MOD_DEC_USE_COUNT;

        if (tape->chrdev_direction == idetape_direction_none)
                MOD_INC_USE_COUNT;
        return 0;
}

/*
 *      Our character device release function.
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp)
{
        ide_drive_t *drive = get_drive_ptr (inode->i_rdev);
        idetape_tape_t *tape = drive->driver_data;
        unsigned int minor=MINOR (inode->i_rdev);
        idetape_pc_t pc;
                        
#if IDETAPE_DEBUG_LOG
        printk (KERN_INFO "Reached idetape_chrdev_release\n");
#endif /* IDETAPE_DEBUG_LOG */

        if (tape->chrdev_direction == idetape_direction_write) {
                idetape_empty_write_pipeline (drive);
                tape->merge_stage = __idetape_kmalloc_stage (tape);
                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_create_write_filemark_cmd (&pc,1);      /* Write a filemark */
                if (idetape_queue_pc_tail (drive,&pc))
                        printk (KERN_ERR "ide-tape: Couldn't write a filemark\n");
        }
        if (tape->chrdev_direction == idetape_direction_read) {
                if (minor < 128)
                        idetape_discard_read_pipeline (drive);
                else
                        idetape_wait_for_pipeline (drive);
        }
        if (tape->cache_stage != NULL) {
                __idetape_kfree_stage (tape->cache_stage);
                tape->cache_stage = NULL;
        }
        if (minor < 128)
                (void) idetape_rewind_tape (drive);

        clear_bit (IDETAPE_BUSY, &tape->flags);
        if (tape->chrdev_direction == idetape_direction_none)
                MOD_DEC_USE_COUNT;
        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 hd_driveid *id)
{
        struct idetape_id_gcw gcw;
#if IDETAPE_INFO_LOG
        unsigned short mask,i;
#endif /* IDETAPE_INFO_LOG */

        if (!id)
                return 0;

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

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

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

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

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

        /* 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;
}

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

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

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,       0,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->min_pipeline,                    NULL);
        ide_add_setting(drive,  "pipeline",     SETTING_RW,     -1,     -1,             TYPE_INT,       0,                      0xffff,                 tape->stage_size / 1024,        1,                              &tape->max_stages,                      NULL);
        ide_add_setting(drive,  "pipeline_max", SETTING_RW,     -1,     -1,             TYPE_INT,       0,                      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,  "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_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)
{
        ide_hwif_t *hwif = HWIF(drive);
        unsigned long t1, tmid, tn, t;
        u16 speed;
        struct idetape_id_gcw gcw;

        drive->driver_data = tape;
        drive->ready_stat = 0;                  /* An ATAPI device ignores DRDY */
#ifdef CONFIG_BLK_DEV_IDEPCI
        /*
         *  These two ide-pci host adapters appear to need this disabled.
         */
        if ((hwif->pci_dev->device == PCI_DEVICE_ID_ARTOP_ATP850UF) ||
            (hwif->pci_dev->device == PCI_DEVICE_ID_TTI_HPT343)) {
                drive->dsc_overlap = 0;
        } else
#endif  /* CONFIG_BLK_DEV_IDEPCI */
        {
                drive->dsc_overlap = 1;
        }
        memset (tape, 0, sizeof (idetape_tape_t));
        tape->drive = drive;
        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->min_pipeline = IDETAPE_MIN_PIPELINE_STAGES;
        tape->max_pipeline = IDETAPE_MAX_PIPELINE_STAGES;
        tape->max_stages = tape->min_pipeline;
        *((unsigned short *) &gcw) = drive->id->config;
        if (gcw.drq_type == 1)
                set_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags);

        idetape_get_mode_sense_results (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;
        }
        tape->pages_per_stage = tape->stage_size / PAGE_SIZE;
        if (tape->stage_size % PAGE_SIZE) {
                tape->pages_per_stage++;
                tape->excess_bh_size = PAGE_SIZE - tape->stage_size % PAGE_SIZE;
        }

        /*
         *      Select the "best" DSC read/write polling frequency.
         *      The following algorithm attempts to find a balance between
         *      good latency and good system throughput. It will be nice to
         *      have all this configurable in run time at some point.
         */
        speed = IDE_MAX (tape->capabilities.speed, tape->capabilities.max_speed);
        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) {
                if (drive->using_dma)
                        t = tmid;
                else {
                        if (hwif->drives[drive->select.b.unit ^ 1].present || hwif->next != hwif)
                                t = (tn + tmid) / 2;
                        else
                                t = tn;
                }
        } else
                t = t1;
        t = IDE_MIN (t, tmid);

        /*
         *      Ensure that the number we got makes sense.
         */
        tape->best_dsc_rw_frequency = IDE_MAX (IDE_MIN (t, IDETAPE_DSC_RW_MAX), IDETAPE_DSC_RW_MIN);
        if (tape->best_dsc_rw_frequency != t) {
                printk (KERN_NOTICE "ide-tape: Although the recommended polling period is %lu jiffies\n", t);
                printk (KERN_NOTICE "ide-tape: we will use %lu jiffies\n", tape->best_dsc_rw_frequency);
        }
        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 int idetape_cleanup (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int minor = tape->minor;
        unsigned long flags;

        save_flags (flags);     /* all CPUs (overkill?) */
        cli();                  /* all CPUs (overkill?) */
        if (test_bit (IDETAPE_BUSY, &tape->flags) || tape->first_stage != NULL || tape->merge_stage_size || drive->usage) {
                restore_flags(flags);   /* all CPUs (overkill?) */
                return 1;
        }
        idetape_chrdevs[minor].drive = NULL;
        restore_flags (flags);  /* all CPUs (overkill?) */
        DRIVER(drive)->busy = 0;
        (void) ide_unregister_subdriver (drive);
        drive->driver_data = NULL;
        kfree (tape);
        for (minor = 0; minor < MAX_HWIFS * MAX_DRIVES; minor++)
                if (idetape_chrdevs[minor].drive != NULL)
                        return 0;
        unregister_chrdev (IDETAPE_MAJOR, "ht");
        idetape_chrdev_present = 0;
        return 0;
}

#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[] = {
        { "name",       S_IFREG|S_IRUGO,        proc_idetape_read_name, NULL },
        { NULL, 0, NULL, NULL }
};

#else

#define idetape_proc    NULL

#endif

/*
 *      IDE subdriver functions, registered with ide.c
 */
static ide_driver_t idetape_driver = {
        "ide-tape",             /* name */
        IDETAPE_VERSION,        /* version */
        ide_tape,               /* media */
        1,                      /* busy */
        1,                      /* supports_dma */
        1,                      /* supports_dsc_overlap */
        idetape_cleanup,        /* cleanup */
        idetape_do_request,     /* do_request */
        idetape_end_request,    /* end_request */
        idetape_blkdev_ioctl,   /* ioctl */
        idetape_blkdev_open,    /* open */
        idetape_blkdev_release, /* release */
        NULL,                   /* media_change */
        idetape_pre_reset,      /* pre_reset */
        NULL,                   /* capacity */
        NULL,                   /* special */
        idetape_proc            /* proc */
};

int idetape_init (void);
static ide_module_t idetape_module = {
        IDE_DRIVER_MODULE,
        idetape_init,
        &idetape_driver,
        NULL
};

/*
 *      Our character device supporting functions, passed to register_chrdev.
 */
static struct file_operations idetape_fops = {
        NULL,                   /* lseek - default */
        idetape_chrdev_read,    /* read  */
        idetape_chrdev_write,   /* write */
        NULL,                   /* readdir - bad */
        NULL,                   /* poll */
        idetape_chrdev_ioctl,   /* ioctl */
        NULL,                   /* mmap */
        idetape_chrdev_open,    /* open */
        NULL,                   /* flush */
        idetape_chrdev_release, /* release */
        NULL,                   /* fsync */
        NULL,                   /* fasync */
        NULL,                   /* check_media_change */
        NULL                    /* revalidate */
};

/*
 *      idetape_init will register the driver for each tape.
 */
int idetape_init (void)
{
        ide_drive_t *drive;
        idetape_tape_t *tape;
        int minor, failed = 0, supported = 0;

        MOD_INC_USE_COUNT;
        if (!idetape_chrdev_present)
                for (minor = 0; minor < MAX_HWIFS * MAX_DRIVES; minor++ )
                        idetape_chrdevs[minor].drive = NULL;

        if ((drive = ide_scan_devices (ide_tape, idetape_driver.name, NULL, failed++)) == NULL) {
                ide_register_module (&idetape_module);
                MOD_DEC_USE_COUNT;
                return 0;
        }
        if (!idetape_chrdev_present && register_chrdev (IDETAPE_MAJOR, "ht", &idetape_fops)) {
                printk (KERN_ERR "ide-tape: Failed to register character device interface\n");
                MOD_DEC_USE_COUNT;
                return -EBUSY;
        }
        do {
                if (!idetape_identify_device (drive, drive->id)) {
                        printk (KERN_ERR "ide-tape: %s: not supported by this version of ide-tape\n", drive->name);
                        continue;
                }
                tape = (idetape_tape_t *) kmalloc (sizeof (idetape_tape_t), GFP_KERNEL);
                if (tape == NULL) {
                        printk (KERN_ERR "ide-tape: %s: Can't allocate a tape structure\n", drive->name);
                        continue;
                }
                if (ide_register_subdriver (drive, &idetape_driver, IDE_SUBDRIVER_VERSION)) {
                        printk (KERN_ERR "ide-tape: %s: Failed to register the driver with ide.c\n", drive->name);
                        kfree (tape);
                        continue;
                }
                for (minor = 0; idetape_chrdevs[minor].drive != NULL; minor++);
                idetape_setup (drive, tape, minor);
                idetape_chrdevs[minor].drive = drive;
                supported++; failed--;
        } while ((drive = ide_scan_devices (ide_tape, idetape_driver.name, NULL, failed++)) != NULL);
        if (!idetape_chrdev_present && !supported) {
                unregister_chrdev (IDETAPE_MAJOR, "ht");
        } else
                idetape_chrdev_present = 1;
        ide_register_module (&idetape_module);
        MOD_DEC_USE_COUNT;
        return 0;
}

#ifdef MODULE
int init_module (void)
{
        return idetape_init ();
}

void cleanup_module (void)
{
        ide_drive_t *drive;
        int minor;

        for (minor = 0; minor < MAX_HWIFS * MAX_DRIVES; minor++) {
                drive = idetape_chrdevs[minor].drive;
                if (drive) {
                        if (idetape_cleanup (drive))
                                printk (KERN_ERR "ide-tape: %s: cleanup_module() called while still busy\n", drive->name);
                        /* We must remove proc entries defined in this module.
                           Otherwise we oops while accessing these entries */
                        if (drive->proc)
                                ide_remove_proc_entries(drive->proc, idetape_proc);
                }
        }
        ide_unregister_module(&idetape_module);
}
#endif /* MODULE */