Merge branch 'for-linus' of master.kernel.org:/home/rmk/linux-2.6-arm

[sfrench/cifs-2.6.git] / drivers / ide / ide-tape.c

/*
 * IDE ATAPI streaming tape driver.
 *
 * Copyright (C) 1995-1999  Gadi Oxman <gadio@netvision.net.il>
 * Copyright (C) 2003-2005  Bartlomiej Zolnierkiewicz
 *
 * 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).
 *
 * For a historical changelog see
 * Documentation/ide/ChangeLog.ide-tape.1995-2002
 */

#define IDETAPE_VERSION "1.19"

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

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

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


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

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

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

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

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

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

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

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

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

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

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

struct idetape_bh {
        u32 b_size;
        atomic_t b_count;
        struct idetape_bh *b_reqnext;
        char *b_data;
};

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

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

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

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

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

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

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

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

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

        /*
         *      Device information
         */
        /* Usually 512 or 1024 bytes */
        unsigned short tape_block_size;
        int user_bs_factor;

        /* Copy of the tape's Capabilities and Mechanical Page */
        u8 caps[20];

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

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

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

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

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

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

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

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

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

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

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

static DEFINE_MUTEX(idetape_ref_mutex);

static struct class *idetape_sysfs_class;

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

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

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

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

static void ide_tape_release(struct kref *);

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

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

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

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

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

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

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

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

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

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

/*
 *      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;

/* Structures related to the SELECT SENSE / MODE SENSE packet commands. */
#define IDETAPE_BLOCK_DESCRIPTOR        0
#define IDETAPE_CAPABILITIES_PAGE       0x2a

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/*
 * 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, u8 *sense)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->failed_pc;

        tape->sense_key = sense[2] & 0xF;
        tape->asc       = sense[12];
        tape->ascq      = sense[13];
#if IDETAPE_DEBUG_LOG
        /*
         * Without debugging, we only log an error if we decided to give up
         * retrying.
         */
        if (tape->debug_level >= 1)
                printk(KERN_INFO "ide-tape: pc = %x, sense key = %x, "
                        "asc = %x, ascq = %x\n",
                        pc->c[0], tape->sense_key,
                        tape->asc, tape->ascq);
#endif /* IDETAPE_DEBUG_LOG */

        /* Correct pc->actually_transferred by asking the tape.  */
        if (test_bit(PC_DMA_ERROR, &pc->flags)) {
                pc->actually_transferred = pc->request_transfer -
                        tape->tape_block_size *
                        be32_to_cpu(get_unaligned((u32 *)&sense[3]));
                idetape_update_buffers(pc);
        }

        /*
         * If error was the result of a zero-length read or write command,
         * with sense key=5, asc=0x22, ascq=0, let it slide.  Some drives
         * (i.e. Seagate STT3401A Travan) don't support 0-length read/writes.
         */
        if ((pc->c[0] == READ_6 || pc->c[0] == WRITE_6)
            /* length == 0 */
            && pc->c[4] == 0 && pc->c[3] == 0 && pc->c[2] == 0) {
                if (tape->sense_key == 5) {
                        /* don't report an error, everything's ok */
                        pc->error = 0;
                        /* don't retry read/write */
                        set_bit(PC_ABORT, &pc->flags);
                }
        }
        if (pc->c[0] == READ_6 && (sense[2] & 0x80)) {
                pc->error = IDETAPE_ERROR_FILEMARK;
                set_bit(PC_ABORT, &pc->flags);
        }
        if (pc->c[0] == WRITE_6) {
                if ((sense[2] & 0x40) || (tape->sense_key == 0xd
                     && tape->asc == 0x0 && tape->ascq == 0x2)) {
                        pc->error = IDETAPE_ERROR_EOD;
                        set_bit(PC_ABORT, &pc->flags);
                }
        }
        if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
                if (tape->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_activate_next_stage(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage = tape->next_stage;
        struct request *rq = &stage->rq;

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

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

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

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

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

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

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

/*
 *      idetape_remove_stage_head removes tape->first_stage from the pipeline.
 *      The caller should avoid race conditions.
 */
static void idetape_remove_stage_head (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *stage;
        
#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 4)
                printk(KERN_INFO "ide-tape: Reached idetape_remove_stage_head\n");
#endif /* IDETAPE_DEBUG_LOG */
        if (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;
        }
        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 (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");
        }
}

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

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

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

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

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

        if (!blk_special_request(rq)) {
                ide_end_request(drive, uptodate, nr_sects);
                return 0;
        }

        spin_lock_irqsave(&tape->spinlock, flags);

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

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

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

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

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

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

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

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

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

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

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

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

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

/*
 *      idetape_pc_intr is the usual interrupt handler which will be called
 *      during a packet command. We will transfer some of the data (as
 *      requested by the drive) and will re-point interrupt handler to us.
 *      When data transfer is finished, we will act according to the
 *      algorithm described before idetape_issue_packet_command.
 *
 */
static ide_startstop_t idetape_pc_intr (ide_drive_t *drive)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        unsigned int temp;
#if SIMULATE_ERRORS
        static int error_sim_count = 0;
#endif
        u16 bcount;
        u8 stat, ireason;

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

        /* Clear the interrupt */
        stat = hwif->INB(IDE_STATUS_REG);

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

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

        /* No more interrupts */
        if ((stat & DRQ_STAT) == 0) {
#if IDETAPE_DEBUG_LOG
                if (tape->debug_level >= 2)
                        printk(KERN_INFO "ide-tape: Packet command completed, %d bytes transferred\n", pc->actually_transferred);
#endif /* IDETAPE_DEBUG_LOG */
                clear_bit(PC_DMA_IN_PROGRESS, &pc->flags);

                local_irq_enable();

#if SIMULATE_ERRORS
                if ((pc->c[0] == WRITE_6 || pc->c[0] == READ_6) &&
                    (++error_sim_count % 100) == 0) {
                        printk(KERN_INFO "ide-tape: %s: simulating error\n",
                                tape->name);
                        stat |= ERR_STAT;
                }
#endif
                if ((stat & ERR_STAT) && pc->c[0] == REQUEST_SENSE)
                        stat &= ~ERR_STAT;
                if ((stat & ERR_STAT) || test_bit(PC_DMA_ERROR, &pc->flags)) {
                        /* Error detected */
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 1)
                                printk(KERN_INFO "ide-tape: %s: I/O error\n",
                                        tape->name);
#endif /* IDETAPE_DEBUG_LOG */
                        if (pc->c[0] == REQUEST_SENSE) {
                                printk(KERN_ERR "ide-tape: I/O error in request sense command\n");
                                return ide_do_reset(drive);
                        }
#if IDETAPE_DEBUG_LOG
                        if (tape->debug_level >= 1)
                                printk(KERN_INFO "ide-tape: [cmd %x]: check condition\n", pc->c[0]);
#endif
                        /* Retry operation */
                        return idetape_retry_pc(drive);
                }
                pc->error = 0;
                if (test_bit(PC_WAIT_FOR_DSC, &pc->flags) &&
                    (stat & SEEK_STAT) == 0) {
                        /* Media access command */
                        tape->dsc_polling_start = jiffies;
                        tape->dsc_polling_frequency = IDETAPE_DSC_MA_FAST;
                        tape->dsc_timeout = jiffies + IDETAPE_DSC_MA_TIMEOUT;
                        /* Allow ide.c to handle other requests */
                        idetape_postpone_request(drive);
                        return ide_stopped;
                }
                if (tape->failed_pc == pc)
                        tape->failed_pc = NULL;
                /* Command finished - Call the callback function */
                return pc->callback(drive);
        }
        if (test_and_clear_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
                printk(KERN_ERR "ide-tape: The tape wants to issue more "
                                "interrupts in DMA mode\n");
                printk(KERN_ERR "ide-tape: DMA disabled, reverting to PIO\n");
                ide_dma_off(drive);
                return ide_do_reset(drive);
        }
        /* Get the number of bytes to transfer on this interrupt. */
        bcount = (hwif->INB(IDE_BCOUNTH_REG) << 8) |
                  hwif->INB(IDE_BCOUNTL_REG);

        ireason = hwif->INB(IDE_IREASON_REG);

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

/*
 *      Packet Command Interface
 *
 *      The current Packet Command is available in tape->pc, and will not
 *      change until we finish handling it. Each packet command is associated
 *      with a callback function that will be called when the command is
 *      finished.
 *
 *      The handling will be done in three stages:
 *
 *      1.      idetape_issue_packet_command will send the packet command to the
 *              drive, and will set the interrupt handler to idetape_pc_intr.
 *
 *      2.      On each interrupt, idetape_pc_intr will be called. This step
 *              will be repeated until the device signals us that no more
 *              interrupts will be issued.
 *
 *      3.      ATAPI Tape media access commands have immediate status with a
 *              delayed process. In case of a successful initiation of a
 *              media access packet command, the DSC bit will be set when the
 *              actual execution of the command is finished. 
 *              Since the tape drive will not issue an interrupt, we have to
 *              poll for this event. In this case, we define the request as
 *              "low priority request" by setting rq_status to
 *              IDETAPE_RQ_POSTPONED,   set a timer to poll for DSC and exit
 *              the driver.
 *
 *              ide.c will then give higher priority to requests which
 *              originate from the other device, until will change rq_status
 *              to RQ_ACTIVE.
 *
 *      4.      When the packet command is finished, it will be checked for errors.
 *
 *      5.      In case an error was found, we queue a request sense packet
 *              command in front of the request queue and retry the operation
 *              up to IDETAPE_MAX_PC_RETRIES times.
 *
 *      6.      In case no error was found, or we decided to give up and not
 *              to retry again, the callback function will be called and then
 *              we will handle the next request.
 *
 */
static ide_startstop_t idetape_transfer_pc(ide_drive_t *drive)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        int retries = 100;
        ide_startstop_t startstop;
        u8 ireason;

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

static ide_startstop_t idetape_issue_packet_command (ide_drive_t *drive, idetape_pc_t *pc)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        int dma_ok = 0;
        u16 bcount;

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

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

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

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

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

        ide_pktcmd_tf_load(drive, IDE_TFLAG_NO_SELECT_MASK |
                           IDE_TFLAG_OUT_DEVICE, bcount, dma_ok);

        if (dma_ok)                     /* Will begin DMA later */
                set_bit(PC_DMA_IN_PROGRESS, &pc->flags);
        if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
                ide_execute_command(drive, WIN_PACKETCMD, &idetape_transfer_pc,
                                    IDETAPE_WAIT_CMD, NULL);
                return ide_started;
        } else {
                hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
                return idetape_transfer_pc(drive);
        }
}

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

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

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

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

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

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

static ide_startstop_t idetape_media_access_finished (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = tape->pc;
        u8 stat;

        stat = drive->hwif->INB(IDE_STATUS_REG);
        if (stat & SEEK_STAT) {
                if (stat & ERR_STAT) {
                        /* Error detected */
                        if (pc->c[0] != TEST_UNIT_READY)
                                printk(KERN_ERR "ide-tape: %s: I/O error, ",
                                                tape->name);
                        /* Retry operation */
                        return idetape_retry_pc(drive);
                }
                pc->error = 0;
                if (tape->failed_pc == pc)
                        tape->failed_pc = NULL;
        } else {
                pc->error = IDETAPE_ERROR_GENERAL;
                tape->failed_pc = NULL;
        }
        return pc->callback(drive);
}

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

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

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

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

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

static void idetape_create_read_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
        idetape_init_pc(pc);
        pc->c[0] = READ_6;
        put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);
        pc->c[1] = 1;
        pc->callback = &idetape_rw_callback;
        pc->bh = bh;
        atomic_set(&bh->b_count, 0);
        pc->buffer = NULL;
        pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
        if (pc->request_transfer == tape->stage_size)
                set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

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

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

static void idetape_create_write_cmd(idetape_tape_t *tape, idetape_pc_t *pc, unsigned int length, struct idetape_bh *bh)
{
        idetape_init_pc(pc);
        pc->c[0] = WRITE_6;
        put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);
        pc->c[1] = 1;
        pc->callback = &idetape_rw_callback;
        set_bit(PC_WRITING, &pc->flags);
        pc->bh = bh;
        pc->b_data = bh->b_data;
        pc->b_count = atomic_read(&bh->b_count);
        pc->buffer = NULL;
        pc->request_transfer = pc->buffer_size = length * tape->tape_block_size;
        if (pc->request_transfer == tape->stage_size)
                set_bit(PC_DMA_RECOMMENDED, &pc->flags);
}

/*
 * idetape_do_request is our request handling function. 
 */
static ide_startstop_t idetape_do_request(ide_drive_t *drive,
                                          struct request *rq, sector_t block)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t *pc = NULL;
        struct request *postponed_rq = tape->postponed_rq;
        u8 stat;

#if IDETAPE_DEBUG_LOG
        if (tape->debug_level >= 2)
                printk(KERN_INFO "ide-tape: sector: %ld, "
                        "nr_sectors: %ld, current_nr_sectors: %d\n",
                        rq->sector, rq->nr_sectors, rq->current_nr_sectors);
#endif /* IDETAPE_DEBUG_LOG */

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

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

        tape->postponed_rq = NULL;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

static void idetape_create_locate_cmd (ide_drive_t *drive, idetape_pc_t *pc, unsigned int block, u8 partition, int skip)
{
        idetape_init_pc(pc);
        pc->c[0] = POSITION_TO_ELEMENT;
        pc->c[1] = 2;
        put_unaligned(cpu_to_be32(block), (unsigned int *) &pc->c[3]);
        pc->c[8] = partition;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

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

        /* device supports locking according to capabilities page */
        if (!(tape->caps[6] & 0x01))
                return 0;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

static void idetape_create_rewind_cmd (ide_drive_t *drive, idetape_pc_t *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = REZERO_UNIT;
        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] = ERASE;
        pc->c[1] = 1;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

static void idetape_create_space_cmd (idetape_pc_t *pc,int count, u8 cmd)
{
        idetape_init_pc(pc);
        pc->c[0] = SPACE;
        put_unaligned(cpu_to_be32(count), (unsigned int *) &pc->c[1]);
        pc->c[1] = cmd;
        set_bit(PC_WAIT_FOR_DSC, &pc->flags);
        pc->callback = &idetape_pc_callback;
}

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

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

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

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

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

        idetape_switch_buffers(tape, new_stage);
        idetape_add_stage_tail(drive, new_stage);
        tape->pipeline_head++;
        calculate_speeds(drive);

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

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

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

static void idetape_empty_write_pipeline (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int blocks, min;
        struct idetape_bh *bh;

        if (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;
        }
        if (tape->merge_stage_size) {
                blocks = tape->merge_stage_size / tape->tape_block_size;
                if (tape->merge_stage_size % tape->tape_block_size) {
                        unsigned int i;

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

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

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

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

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

static int idetape_initiate_read (ide_drive_t *drive, int max_stages)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_stage_t *new_stage;
        struct request rq;
        int bytes_read;
        u16 blocks = *(u16 *)&tape->caps[12];

        /* Initialize read operation */
        if (tape->chrdev_direction != idetape_direction_read) {
                if (tape->chrdev_direction == idetape_direction_write) {
                        idetape_empty_write_pipeline(drive);
                        idetape_flush_tape_buffers(drive);
                }
                if (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;
                }
                if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                        return -ENOMEM;
                tape->chrdev_direction = idetape_direction_read;

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

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

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

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

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


        if (rq_ptr->errors == IDETAPE_ERROR_EOD)
                return 0;
        else {
                idetape_switch_buffers(tape, tape->first_stage);
                if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
                        set_bit(IDETAPE_FILEMARK, &tape->flags);
                spin_lock_irqsave(&tape->spinlock, flags);
                idetape_remove_stage_head(drive);
                spin_unlock_irqrestore(&tape->spinlock, flags);
                tape->pipeline_head++;
                calculate_speeds(drive);
        }
        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;
        }
        return (bytes_read);
}

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

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

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

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

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

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

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

        struct idetape_config {
                int dsc_rw_frequency;
                int dsc_media_access_frequency;
                int nr_stages;
        } config;

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

/*
 *      idetape_space_over_filemarks is now a bit more complicated than just
 *      passing the command to the tape since we may have crossed some
 *      filemarks during our pipelined read-ahead mode.
 *
 *      As a minor side effect, the pipeline enables us to support MTFSFM when
 *      the filemark is in our internal pipeline even if the tape doesn't
 *      support spacing over filemarks in the reverse direction.
 */
static int idetape_space_over_filemarks (ide_drive_t *drive,short mt_op,int mt_count)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        unsigned long flags;
        int retval,count=0;
        int sprev = !!(tape->caps[4] & 0x20);

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

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

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


/*
 *      Our character device read / write functions.
 *
 *      The tape is optimized to maximize throughput when it is transferring
 *      an integral number of the "continuous transfer limit", which is
 *      a parameter of the specific tape (26 KB on my particular tape).
 *      (32 kB for Onstream)
 *
 *      As of version 1.3 of the driver, the character device provides an
 *      abstract continuous view of the media - any mix of block sizes (even 1
 *      byte) on the same backup/restore procedure is supported. The driver
 *      will internally convert the requests to the recommended transfer unit,
 *      so that an unmatch between the user's block size to the recommended
 *      size will only result in a (slightly) increased driver overhead, but
 *      will no longer hit performance.
 *      This is not applicable to Onstream.
 */
static ssize_t idetape_chrdev_read (struct file *file, char __user *buf,
                                    size_t count, loff_t *ppos)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        ssize_t bytes_read,temp, actually_read = 0, rc;
        ssize_t ret = 0;
        u16 ctl = *(u16 *)&tape->caps[12];

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

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

        return (ret) ? ret : actually_read;
}

static ssize_t idetape_chrdev_write (struct file *file, const char __user *buf,
                                     size_t count, loff_t *ppos)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        ssize_t actually_written = 0;
        ssize_t ret = 0;
        u16 ctl = *(u16 *)&tape->caps[12];

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

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

        /* Initialize write operation */
        if (tape->chrdev_direction != idetape_direction_write) {
                if (tape->chrdev_direction == idetape_direction_read)
                        idetape_discard_read_pipeline(drive, 1);
                if (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;
                }
                if ((tape->merge_stage = __idetape_kmalloc_stage(tape, 0, 0)) == NULL)
                        return -ENOMEM;
                tape->chrdev_direction = idetape_direction_write;
                idetape_init_merge_stage(tape);

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

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

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

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

/*
 * Called from idetape_chrdev_ioctl when the general mtio MTIOCTOP ioctl is
 * requested.
 *
 * Note: MTBSF and MTBSFM are not supported when the tape doesn't support
 * spacing over filemarks in the reverse direction. In this case, MTFSFM is also
 * usually not supported (it is supported in the rare case in which we crossed
 * the filemark during our read-ahead pipelined operation mode).
 *
 * The following commands are currently not supported:
 *
 * MTFSS, MTBSS, MTWSM, MTSETDENSITY, MTSETDRVBUFFER, MT_ST_BOOLEANS,
 * MT_ST_WRITE_THRESHOLD.
 */
static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;
        int i,retval;

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

/*
 * Our character device ioctls. General mtio.h magnetic io commands are
 * supported here, and not in the corresponding block interface. Our own
 * ide-tape ioctls are supported on both interfaces.
 */
static int idetape_chrdev_ioctl(struct inode *inode, struct file *file,
                                unsigned int cmd, unsigned long arg)
{
        struct ide_tape_obj *tape = ide_tape_f(file);
        ide_drive_t *drive = tape->drive;
        struct mtop mtop;
        struct mtget mtget;
        struct mtpos mtpos;
        int block_offset = 0, position = tape->first_frame_position;
        void __user *argp = (void __user *)arg;

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

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

/*
 * Do a mode sense page 0 with block descriptor and if it succeeds set the tape
 * block size with the reported value.
 */
static void ide_tape_get_bsize_from_bdesc(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;

        idetape_create_mode_sense_cmd(&pc, IDETAPE_BLOCK_DESCRIPTOR);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: Can't get block descriptor\n");
                if (tape->tape_block_size == 0) {
                        printk(KERN_WARNING "ide-tape: Cannot deal with zero "
                                            "block size, assuming 32k\n");
                        tape->tape_block_size = 32768;
                }
                return;
        }
        tape->tape_block_size = (pc.buffer[4 + 5] << 16) +
                                (pc.buffer[4 + 6] << 8)  +
                                 pc.buffer[4 + 7];
        tape->drv_write_prot = (pc.buffer[2] & 0x80) >> 7;
}

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

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

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

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

        drive = tape->drive;

        filp->private_data = tape;

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

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

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

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

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

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

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

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

out_put_tape:
        ide_tape_put(tape);
        return retval;
}

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

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

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

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

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

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

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

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

        /* Check that we can support this device */

        if (gcw.protocol != 2)
                printk(KERN_ERR "ide-tape: Protocol (0x%02x) is not ATAPI\n",
                                gcw.protocol);
        else if (gcw.device_type != 1)
                printk(KERN_ERR "ide-tape: Device type (0x%02x) is not set "
                                "to tape\n", gcw.device_type);
        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 (0x%02x) is not 12 "
                                "bytes long\n", gcw.packet_size);
        } else
                return 1;
        return 0;
}

static void idetape_get_inquiry_results(ide_drive_t *drive)
{
        char *r;
        idetape_tape_t *tape = drive->driver_data;
        idetape_pc_t pc;

        idetape_create_inquiry_cmd(&pc);
        if (idetape_queue_pc_tail(drive, &pc)) {
                printk(KERN_ERR "ide-tape: %s: can't get INQUIRY results\n",
                                tape->name);
                return;
        }
        memcpy(tape->vendor_id, &pc.buffer[8], 8);
        memcpy(tape->product_id, &pc.buffer[16], 16);
        memcpy(tape->firmware_revision, &pc.buffer[32], 4);

        ide_fixstring(tape->vendor_id, 10, 0);
        ide_fixstring(tape->product_id, 18, 0);
        ide_fixstring(tape->firmware_revision, 6, 0);
        r = tape->firmware_revision;
        if (*(r + 1) == '.')
                tape->firmware_revision_num = (*r - '0') * 100 +
                        (*(r + 2) - '0') * 10 + *(r + 3) - '0';
        printk(KERN_INFO "ide-tape: %s <-> %s: %s %s rev %s\n",
                        drive->name, tape->name, tape->vendor_id,
                        tape->product_id, tape->firmware_revision);
}

/*
 * Ask 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;
        u8 *caps;
        u8 speed, max_speed;

        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;
                put_unaligned(52,   (u16 *)&tape->caps[12]);
                put_unaligned(540,  (u16 *)&tape->caps[14]);
                put_unaligned(6*52, (u16 *)&tape->caps[16]);
                return;
        }
        caps = pc.buffer + 4 + pc.buffer[3];

        /* convert to host order and save for later use */
        speed = be16_to_cpu(*(u16 *)&caps[14]);
        max_speed = be16_to_cpu(*(u16 *)&caps[8]);

        put_unaligned(max_speed, (u16 *)&caps[8]);
        put_unaligned(be16_to_cpu(*(u16 *)&caps[12]), (u16 *)&caps[12]);
        put_unaligned(speed, (u16 *)&caps[14]);
        put_unaligned(be16_to_cpu(*(u16 *)&caps[16]), (u16 *)&caps[16]);

        if (!speed) {
                printk(KERN_INFO "ide-tape: %s: invalid tape speed "
                                "(assuming 650KB/sec)\n", drive->name);
                put_unaligned(650, (u16 *)&caps[14]);
        }
        if (!max_speed) {
                printk(KERN_INFO "ide-tape: %s: invalid max_speed "
                                "(assuming 650KB/sec)\n", drive->name);
                put_unaligned(650, (u16 *)&caps[8]);
        }

        memcpy(&tape->caps, caps, 20);
        if (caps[7] & 0x02)
                tape->tape_block_size = 512;
        else if (caps[7] & 0x04)
                tape->tape_block_size = 1024;
}

#ifdef CONFIG_IDE_PROC_FS
static void idetape_add_settings (ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

/*
 *                      drive   setting name            read/write      data type       min                     max                     mul_factor                      div_factor      data pointer                            set function
 */
        ide_add_setting(drive, "buffer", SETTING_READ, TYPE_SHORT, 0, 0xffff,
                        1, 2, (u16 *)&tape->caps[16], NULL);
        ide_add_setting(drive,  "pipeline_min",         SETTING_RW,     TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,              &tape->min_pipeline,                    NULL);
        ide_add_setting(drive,  "pipeline",             SETTING_RW,     TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,              &tape->max_stages,                      NULL);
        ide_add_setting(drive,  "pipeline_max",         SETTING_RW,     TYPE_INT,       1,                      0xffff,                 tape->stage_size / 1024,        1,              &tape->max_pipeline,                    NULL);
        ide_add_setting(drive,  "pipeline_used",        SETTING_READ,   TYPE_INT,       0,                      0xffff,                 tape->stage_size / 1024,        1,              &tape->nr_stages,                       NULL);
        ide_add_setting(drive,  "pipeline_pending",     SETTING_READ,   TYPE_INT,       0,                      0xffff,                 tape->stage_size / 1024,        1,              &tape->nr_pending_stages,               NULL);
        ide_add_setting(drive, "speed", SETTING_READ, TYPE_SHORT, 0, 0xffff,
                        1, 1, (u16 *)&tape->caps[14], NULL);
        ide_add_setting(drive,  "stage",                SETTING_READ,   TYPE_INT,       0,                      0xffff,                 1,                              1024,           &tape->stage_size,                      NULL);
        ide_add_setting(drive,  "tdsc",                 SETTING_RW,     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,     TYPE_BYTE,      0,                      1,                      1,                              1,              &drive->dsc_overlap,                    NULL);
        ide_add_setting(drive,  "pipeline_head_speed_c",SETTING_READ,   TYPE_INT,       0,                      0xffff,                 1,                              1,              &tape->controlled_pipeline_head_speed,  NULL);
        ide_add_setting(drive,  "pipeline_head_speed_u",SETTING_READ,   TYPE_INT,       0,                      0xffff,                 1,                              1,              &tape->uncontrolled_pipeline_head_speed,NULL);
        ide_add_setting(drive,  "avg_speed",            SETTING_READ,   TYPE_INT,       0,                      0xffff,                 1,                              1,              &tape->avg_speed,                       NULL);
        ide_add_setting(drive,  "debug_level",          SETTING_RW,     TYPE_INT,       0,                      0xffff,                 1,                              1,              &tape->debug_level,                     NULL);
}
#else
static inline void idetape_add_settings(ide_drive_t *drive) { ; }
#endif

/*
 *      ide_setup is called to:
 *
 *              1.      Initialize our various state variables.
 *              2.      Ask the tape for its capabilities.
 *              3.      Allocate a buffer which will be used for data
 *                      transfer. The buffer size is chosen based on
 *                      the recommendation which we received in step (2).
 *
 *      Note that at this point ide.c already assigned us an irq, so that
 *      we can queue requests here and wait for their completion.
 */
static void idetape_setup (ide_drive_t *drive, idetape_tape_t *tape, int minor)
{
        unsigned long t1, tmid, tn, t;
        int speed;
        struct idetape_id_gcw gcw;
        int stage_size;
        struct sysinfo si;
        u16 *ctl = (u16 *)&tape->caps[12];

        spin_lock_init(&tape->spinlock);
        drive->dsc_overlap = 1;
        if (drive->hwif->host_flags & IDE_HFLAG_NO_DSC) {
                printk(KERN_INFO "ide-tape: %s: disabling DSC overlap\n",
                                 tape->name);
                drive->dsc_overlap = 0;
        }
        /* Seagate Travan drives do not support DSC overlap. */
        if (strstr(drive->id->model, "Seagate STT3401"))
                drive->dsc_overlap = 0;
        tape->minor = minor;
        tape->name[0] = 'h';
        tape->name[1] = 't';
        tape->name[2] = '0' + minor;
        tape->chrdev_direction = idetape_direction_none;
        tape->pc = tape->pc_stack;
        tape->max_insert_speed = 10000;
        tape->speed_control = 1;
        *((unsigned short *) &gcw) = drive->id->config;
        if (gcw.drq_type == 1)
                set_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags);

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

        /* Select the "best" DSC read/write polling freq and pipeline size. */
        speed = max(*(u16 *)&tape->caps[14], *(u16 *)&tape->caps[8]);

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

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

        t1 = (tape->stage_size * HZ) / (speed * 1000);
        tmid = (*(u16 *)&tape->caps[16] * 32 * HZ) / (speed * 125);
        tn = (IDETAPE_FIFO_THRESHOLD * tape->stage_size * HZ) / (speed * 1000);

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

        /*
         *      Ensure that the number we got makes sense; limit
         *      it within IDETAPE_DSC_RW_MIN and IDETAPE_DSC_RW_MAX.
         */
        tape->best_dsc_rw_frequency = max_t(unsigned long, min_t(unsigned long, t, IDETAPE_DSC_RW_MAX), IDETAPE_DSC_RW_MIN);
        printk(KERN_INFO "ide-tape: %s <-> %s: %dKBps, %d*%dkB buffer, "
                "%dkB pipeline, %lums tDSC%s\n",
                drive->name, tape->name, *(u16 *)&tape->caps[14],
                (*(u16 *)&tape->caps[16] * 512) / tape->stage_size,
                tape->stage_size / 1024,
                tape->max_stages * tape->stage_size / 1024,
                tape->best_dsc_rw_frequency * 1000 / HZ,
                drive->using_dma ? ", DMA":"");

        idetape_add_settings(drive);
}

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

        ide_proc_unregister_driver(drive, tape->driver);

        ide_unregister_region(tape->disk);

        ide_tape_put(tape);
}

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

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

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

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

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

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

static int ide_tape_probe(ide_drive_t *);

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

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

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

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

        return 0;
}

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

        ide_tape_put(tape);

        return 0;
}

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

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

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

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

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

        ide_init_disk(g, drive);

        ide_proc_register_driver(drive, &idetape_driver);

        kref_init(&tape->kref);

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

        g->private_data = &tape->driver;

        drive->driver_data = tape;

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

        idetape_setup(drive, tape, minor);

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

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

        return 0;

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

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

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

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

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

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

        return 0;

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

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