ide-tape: mv tape->merge_stage_size tape->merge_bh_size

[linux-2.6-omap-h63xx.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 "1.20"

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

enum {
        /* output errors only */
        DBG_ERR =               (1 << 0),
        /* output all sense key/asc */
        DBG_SENSE =             (1 << 1),
        /* info regarding all chrdev-related procedures */
        DBG_CHRDEV =            (1 << 2),
        /* all remaining procedures */
        DBG_PROCS =             (1 << 3),
        /* buffer alloc info (pc_stack & rq_stack) */
        DBG_PCRQ_STACK =        (1 << 4),
};

/* define to see debug info */
#define IDETAPE_DEBUG_LOG               0

#if IDETAPE_DEBUG_LOG
#define debug_log(lvl, fmt, args...)                    \
{                                                       \
        if (tape->debug_mask & lvl)                     \
        printk(KERN_INFO "ide-tape: " fmt, ## args);    \
}
#else
#define debug_log(lvl, fmt, args...) do {} while (0)
#endif

/**************************** Tunable parameters *****************************/
/*
 * 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 could service requests from the other device
 * on the same interface in the meantime.
 *
 * 2. After the successful initialization of a "media access packet command",
 * which is a command that can take a long time to complete (the interval can
 * range from several seconds to 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
 * (1 second), and if we don't receive DSC after IDETAPE_DSC_MA_THRESHOLD
 * (5 min), we switch it to a lower frequency - IDETAPE_DSC_MA_SLOW (1 min).
 *
 * 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

/* tape directions */
enum {
        IDETAPE_DIR_NONE  = (1 << 0),
        IDETAPE_DIR_READ  = (1 << 1),
        IDETAPE_DIR_WRITE = (1 << 2),
};

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

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

/* 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),
};

/* Error codes 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

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

/* Tape flag bits values. */
enum {
        IDETAPE_FLAG_IGNORE_DSC         = (1 << 0),
        /* 0 When the tape position is unknown */
        IDETAPE_FLAG_ADDRESS_VALID      = (1 << 1),
        /* Device already opened */
        IDETAPE_FLAG_BUSY               = (1 << 2),
        /* Attempt to auto-detect the current user block size */
        IDETAPE_FLAG_DETECT_BS          = (1 << 3),
        /* Currently on a filemark */
        IDETAPE_FLAG_FILEMARK           = (1 << 4),
        /* DRQ interrupt device */
        IDETAPE_FLAG_DRQ_INTERRUPT      = (1 << 5),
        /* 0 = no tape is loaded, so we don't rewind after ejecting */
        IDETAPE_FLAG_MEDIUM_PRESENT     = (1 << 6),
};

/* 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 the struct 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 */
        struct ide_atapi_pc *pc;
        /* Last failed packet command */
        struct ide_atapi_pc *failed_pc;
        /* Packet command stack */
        struct ide_atapi_pc 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.
         */
        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_freq;
        unsigned long dsc_poll_freq;
        unsigned long dsc_timeout;

        /* Read position information */
        u8 partition;
        /* Current block */
        unsigned int first_frame;

        /* 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 */
        u8 chrdev_dir;

        /* tape block size, usually 512 or 1024 bytes */
        unsigned short blk_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.
         */

        /* Data buffer size chosen based on the tape's recommendation */
        int buffer_size;
        idetape_stage_t *merge_stage;
        /* size of the merge buffer */
        int merge_bh_size;
        struct idetape_bh *bh;
        char *b_data;
        int b_count;

        int pages_per_buffer;
        /* 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 lock;

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

        /* 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;

        u32 debug_mask;
} 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);
}

/*
 * 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;
}

static void idetape_input_buffers(ide_drive_t *drive, struct ide_atapi_pc *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");
                        ide_atapi_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, struct ide_atapi_pc *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 %s\n",
                                        __func__);
                        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) {
                        bh = bh->b_reqnext;
                        pc->bh = bh;
                        if (bh) {
                                pc->b_data = bh->b_data;
                                pc->b_count = atomic_read(&bh->b_count);
                        }
                }
        }
}

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

        if (pc->flags & PC_FLAG_WRITING)
                return;
        while (bcount) {
                if (bh == NULL) {
                        printk(KERN_ERR "ide-tape: bh == NULL in %s\n",
                                        __func__);
                        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 struct ide_atapi_pc *idetape_next_pc_storage(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;

        debug_log(DBG_PCRQ_STACK, "pc_stack_index=%d\n", tape->pc_stack_index);

        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;

        debug_log(DBG_PCRQ_STACK, "rq_stack_index=%d\n", tape->rq_stack_index);

        if (tape->rq_stack_index == IDETAPE_PC_STACK)
                tape->rq_stack_index = 0;
        return (&tape->rq_stack[tape->rq_stack_index++]);
}

static void idetape_init_pc(struct ide_atapi_pc *pc)
{
        memset(pc->c, 0, 12);
        pc->retries = 0;
        pc->flags = 0;
        pc->req_xfer = 0;
        pc->buf = pc->pc_buf;
        pc->buf_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;
        struct ide_atapi_pc *pc = tape->failed_pc;

        tape->sense_key = sense[2] & 0xF;
        tape->asc       = sense[12];
        tape->ascq      = sense[13];

        debug_log(DBG_ERR, "pc = %x, sense key = %x, asc = %x, ascq = %x\n",
                 pc->c[0], tape->sense_key, tape->asc, tape->ascq);

        /* Correct pc->xferred by asking the tape.       */
        if (pc->flags & PC_FLAG_DMA_ERROR) {
                pc->xferred = pc->req_xfer -
                        tape->blk_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 */
                        pc->flags |= PC_FLAG_ABORT;
                }
        }
        if (pc->c[0] == READ_6 && (sense[2] & 0x80)) {
                pc->error = IDETAPE_ERROR_FILEMARK;
                pc->flags |= PC_FLAG_ABORT;
        }
        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;
                        pc->flags |= PC_FLAG_ABORT;
                }
        }
        if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
                if (tape->sense_key == 8) {
                        pc->error = IDETAPE_ERROR_EOD;
                        pc->flags |= PC_FLAG_ABORT;
                }
                if (!(pc->flags & PC_FLAG_ABORT) &&
                    pc->xferred)
                        pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
        }
}

/* Free data buffers completely. */
static void ide_tape_kfree_buffer(idetape_stage_t *stage)
{
        struct idetape_bh *prev_bh, *bh = stage->bh;

        while (bh) {
                u32 size = bh->b_size;

                while (size) {
                        unsigned int order = fls(size >> PAGE_SHIFT)-1;

                        if (bh->b_data)
                                free_pages((unsigned long)bh->b_data, order);

                        size &= (order-1);
                        bh->b_data += (1 << order) * PAGE_SIZE;
                }
                prev_bh = bh;
                bh = bh->b_reqnext;
                kfree(prev_bh);
        }
        kfree(stage);
}

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;

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        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->lock, flags);

        ide_end_drive_cmd(drive, 0, 0);

        spin_unlock_irqrestore(&tape->lock, flags);
        return 0;
}

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

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        if (!tape->pc->error) {
                idetape_analyze_error(drive, tape->pc->buf);
                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(struct ide_atapi_pc *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = REQUEST_SENSE;
        pc->c[4] = 20;
        pc->req_xfer = 20;
        pc->idetape_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;
}

/*
 * Generate 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. The function below is called from the request
 * handling part of the driver (the "bottom" part). Safe storage for the request
 * should be allocated with ide_tape_next_{pc,rq}_storage() prior to that.
 *
 * 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, struct ide_atapi_pc *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;
        struct ide_atapi_pc *pc;
        struct request *rq;

        (void)ide_read_error(drive);
        pc = idetape_next_pc_storage(drive);
        rq = idetape_next_rq_storage(drive);
        idetape_create_request_sense_cmd(pc);
        set_bit(IDETAPE_FLAG_IGNORE_DSC, &tape->flags);
        idetape_queue_pc_head(drive, pc, rq);
        return ide_stopped;
}

/*
 * Postpone 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;

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

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

typedef void idetape_io_buf(ide_drive_t *, struct ide_atapi_pc *, unsigned int);

/*
 * This 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_pc.
 */
static ide_startstop_t idetape_pc_intr(ide_drive_t *drive)
{
        ide_hwif_t *hwif = drive->hwif;
        idetape_tape_t *tape = drive->driver_data;
        struct ide_atapi_pc *pc = tape->pc;
        xfer_func_t *xferfunc;
        idetape_io_buf *iobuf;
        unsigned int temp;
#if SIMULATE_ERRORS
        static int error_sim_count;
#endif
        u16 bcount;
        u8 stat, ireason;

        debug_log(DBG_PROCS, "Enter %s - interrupt handler\n", __func__);

        /* Clear the interrupt */
        stat = ide_read_status(drive);

        if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
                if (hwif->dma_ops->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)
                         */
                        pc->flags |= PC_FLAG_DMA_ERROR;
                } else {
                        pc->xferred = pc->req_xfer;
                        idetape_update_buffers(pc);
                }
                debug_log(DBG_PROCS, "DMA finished\n");

        }

        /* No more interrupts */
        if ((stat & DRQ_STAT) == 0) {
                debug_log(DBG_SENSE, "Packet command completed, %d bytes"
                                " transferred\n", pc->xferred);

                pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;
                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) || (pc->flags & PC_FLAG_DMA_ERROR)) {
                        /* Error detected */
                        debug_log(DBG_ERR, "%s: I/O error\n", tape->name);

                        if (pc->c[0] == REQUEST_SENSE) {
                                printk(KERN_ERR "ide-tape: I/O error in request"
                                                " sense command\n");
                                return ide_do_reset(drive);
                        }
                        debug_log(DBG_ERR, "[cmd %x]: check condition\n",
                                        pc->c[0]);

                        /* Retry operation */
                        return idetape_retry_pc(drive);
                }
                pc->error = 0;
                if ((pc->flags & PC_FLAG_WAIT_FOR_DSC) &&
                    (stat & SEEK_STAT) == 0) {
                        /* Media access command */
                        tape->dsc_polling_start = jiffies;
                        tape->dsc_poll_freq = 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->idetape_callback(drive);
        }

        if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
                pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;
                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(hwif->io_ports.lbah_addr) << 8) |
                  hwif->INB(hwif->io_ports.lbam_addr);

        ireason = hwif->INB(hwif->io_ports.nsect_addr);

        if (ireason & CD) {
                printk(KERN_ERR "ide-tape: CoD != 0 in %s\n", __func__);
                return ide_do_reset(drive);
        }
        if (((ireason & IO) == IO) == !!(pc->flags & PC_FLAG_WRITING)) {
                /* 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 (!(pc->flags & PC_FLAG_WRITING)) {
                /* Reading - Check that we have enough space */
                temp = pc->xferred + bcount;
                if (temp > pc->req_xfer) {
                        if (temp > pc->buf_size) {
                                printk(KERN_ERR "ide-tape: The tape wants to "
                                        "send us more data than expected "
                                        "- discarding data\n");
                                ide_atapi_discard_data(drive, bcount);
                                ide_set_handler(drive, &idetape_pc_intr,
                                                IDETAPE_WAIT_CMD, NULL);
                                return ide_started;
                        }
                        debug_log(DBG_SENSE, "The tape wants to send us more "
                                "data than expected - allowing transfer\n");
                }
                iobuf = &idetape_input_buffers;
                xferfunc = hwif->atapi_input_bytes;
        } else {
                iobuf = &idetape_output_buffers;
                xferfunc = hwif->atapi_output_bytes;
        }

        if (pc->bh)
                iobuf(drive, pc, bcount);
        else
                xferfunc(drive, pc->cur_pos, bcount);

        /* Update the current position */
        pc->xferred += bcount;
        pc->cur_pos += bcount;

        debug_log(DBG_SENSE, "[cmd %x] transferred %d bytes on that intr.\n",
                        pc->c[0], bcount);

        /* 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_pc 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;
        struct ide_atapi_pc *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(hwif->io_ports.nsect_addr);
        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(hwif->io_ports.nsect_addr);
                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 (pc->flags & PC_FLAG_DMA_IN_PROGRESS)
                hwif->dma_ops->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_pc(ide_drive_t *drive,
                struct ide_atapi_pc *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 ||
                (pc->flags & PC_FLAG_ABORT)) {
                /*
                 * We will "abort" retrying a packet command in case legitimate
                 * error code was received (crossing a filemark, or end of the
                 * media, for example).
                 */
                if (!(pc->flags & PC_FLAG_ABORT)) {
                        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->idetape_callback(drive);
        }
        debug_log(DBG_SENSE, "Retry #%d, cmd = %02X\n", pc->retries, pc->c[0]);

        pc->retries++;
        /* We haven't transferred any data yet */
        pc->xferred = 0;
        pc->cur_pos = pc->buf;
        /* Request to transfer the entire buffer at once */
        bcount = pc->req_xfer;

        if (pc->flags & PC_FLAG_DMA_ERROR) {
                pc->flags &= ~PC_FLAG_DMA_ERROR;
                printk(KERN_WARNING "ide-tape: DMA disabled, "
                                "reverting to PIO\n");
                ide_dma_off(drive);
        }
        if ((pc->flags & PC_FLAG_DMA_RECOMMENDED) && drive->using_dma)
                dma_ok = !hwif->dma_ops->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 */
                pc->flags |= PC_FLAG_DMA_IN_PROGRESS;
        if (test_bit(IDETAPE_FLAG_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, hwif->io_ports.command_addr);
                return idetape_transfer_pc(drive);
        }
}

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

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        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(struct ide_atapi_pc *pc, u8 page_code)
{
        idetape_init_pc(pc);
        pc->c[0] = MODE_SENSE;
        if (page_code != IDETAPE_BLOCK_DESCRIPTOR)
                /* DBD = 1 - Don't return block descriptors */
                pc->c[1] = 8;
        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;
        /* We will just discard data in that case */
        pc->c[4] = 255;
        if (page_code == IDETAPE_BLOCK_DESCRIPTOR)
                pc->req_xfer = 12;
        else if (page_code == IDETAPE_CAPABILITIES_PAGE)
                pc->req_xfer = 24;
        else
                pc->req_xfer = 50;
        pc->idetape_callback = &idetape_pc_callback;
}

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

        stat = ide_read_status(drive);

        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->idetape_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->xferred / tape->blk_size;

        tape->avg_size += blocks * tape->blk_size;

        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;
        }
        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        tape->first_frame += 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,
                struct ide_atapi_pc *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->idetape_callback = &idetape_rw_callback;
        pc->bh = bh;
        atomic_set(&bh->b_count, 0);
        pc->buf = NULL;
        pc->buf_size = length * tape->blk_size;
        pc->req_xfer = pc->buf_size;
        if (pc->req_xfer == tape->buffer_size)
                pc->flags |= PC_FLAG_DMA_RECOMMENDED;
}

static void idetape_create_write_cmd(idetape_tape_t *tape,
                struct ide_atapi_pc *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->idetape_callback = &idetape_rw_callback;
        pc->flags |= PC_FLAG_WRITING;
        pc->bh = bh;
        pc->b_data = bh->b_data;
        pc->b_count = atomic_read(&bh->b_count);
        pc->buf = NULL;
        pc->buf_size = length * tape->blk_size;
        pc->req_xfer = pc->buf_size;
        if (pc->req_xfer == tape->buffer_size)
                pc->flags |= PC_FLAG_DMA_RECOMMENDED;
}

static ide_startstop_t idetape_do_request(ide_drive_t *drive,
                                          struct request *rq, sector_t block)
{
        idetape_tape_t *tape = drive->driver_data;
        struct ide_atapi_pc *pc = NULL;
        struct request *postponed_rq = tape->postponed_rq;
        u8 stat;

        debug_log(DBG_SENSE, "sector: %ld, nr_sectors: %ld,"
                        " current_nr_sectors: %d\n",
                        rq->sector, rq->nr_sectors, rq->current_nr_sectors);

        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 && tape->pc->c[0] == REQUEST_SENSE)
                return idetape_issue_pc(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 = ide_read_status(drive);

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

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

        if (!test_and_clear_bit(IDETAPE_FLAG_IGNORE_DSC, &tape->flags) &&
            (stat & SEEK_STAT) == 0) {
                if (postponed_rq == NULL) {
                        tape->dsc_polling_start = jiffies;
                        tape->dsc_poll_freq = tape->best_dsc_rw_freq;
                        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_poll_freq = IDETAPE_DSC_MA_SLOW;
                idetape_postpone_request(drive);
                return ide_stopped;
        }
        if (rq->cmd[0] & REQ_IDETAPE_READ) {
                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) {
                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_PC1) {
                pc = (struct ide_atapi_pc *) 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_pc(drive, pc);
}

/*
 * The function below uses __get_free_pages to allocate a data buffer of size
 * tape->buffer_size (or a bit more). We attempt to combine sequential pages as
 * much as possible.
 *
 * It returns a pointer to the newly allocated buffer, or NULL in case of
 * failure.
 */
static idetape_stage_t *ide_tape_kmalloc_buffer(idetape_tape_t *tape, int full,
                                                int clear)
{
        idetape_stage_t *stage;
        struct idetape_bh *prev_bh, *bh;
        int pages = tape->pages_per_buffer;
        unsigned int order, b_allocd;
        char *b_data = NULL;

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

        stage->bh = kmalloc(sizeof(struct idetape_bh), GFP_KERNEL);
        bh = stage->bh;
        if (bh == NULL)
                goto abort;

        order = fls(pages) - 1;
        bh->b_data = (char *) __get_free_pages(GFP_KERNEL, order);
        if (!bh->b_data)
                goto abort;
        b_allocd = (1 << order) * PAGE_SIZE;
        pages &= (order-1);

        if (clear)
                memset(bh->b_data, 0, b_allocd);
        bh->b_reqnext = NULL;
        bh->b_size = b_allocd;
        atomic_set(&bh->b_count, full ? bh->b_size : 0);

        while (pages) {
                order = fls(pages) - 1;
                b_data = (char *) __get_free_pages(GFP_KERNEL, order);
                if (!b_data)
                        goto abort;
                b_allocd = (1 << order) * PAGE_SIZE;

                if (clear)
                        memset(b_data, 0, b_allocd);

                /* newly allocated page frames below buffer header or ...*/
                if (bh->b_data == b_data + b_allocd) {
                        bh->b_size += b_allocd;
                        bh->b_data -= b_allocd;
                        if (full)
                                atomic_add(b_allocd, &bh->b_count);
                        continue;
                }
                /* they are above the header */
                if (b_data == bh->b_data + bh->b_size) {
                        bh->b_size += b_allocd;
                        if (full)
                                atomic_add(b_allocd, &bh->b_count);
                        continue;
                }
                prev_bh = bh;
                bh = kmalloc(sizeof(struct idetape_bh), GFP_KERNEL);
                if (!bh) {
                        free_pages((unsigned long) b_data, order);
                        goto abort;
                }
                bh->b_reqnext = NULL;
                bh->b_data = b_data;
                bh->b_size = b_allocd;
                atomic_set(&bh->b_count, full ? bh->b_size : 0);
                prev_bh->b_reqnext = bh;

                pages &= (order-1);
        }

        bh->b_size -= tape->excess_bh_size;
        if (full)
                atomic_sub(tape->excess_bh_size, &bh->b_count);
        return stage;
abort:
        ide_tape_kfree_buffer(stage);
        return NULL;
}

static int idetape_copy_stage_from_user(idetape_tape_t *tape,
                                        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 %s\n",
                                        __func__);
                        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,
                                      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 %s\n",
                                        __func__);
                        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) {
                        bh = bh->b_reqnext;
                        tape->bh = bh;
                        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_dir == IDETAPE_DIR_WRITE)
                atomic_set(&bh->b_count, 0);
        else {
                tape->b_data = bh->b_data;
                tape->b_count = atomic_read(&bh->b_count);
        }
}

static ide_startstop_t idetape_read_position_callback(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        u8 *readpos = tape->pc->buf;

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        if (!tape->pc->error) {
                debug_log(DBG_SENSE, "BOP - %s\n",
                                (readpos[0] & 0x80) ? "Yes" : "No");
                debug_log(DBG_SENSE, "EOP - %s\n",
                                (readpos[0] & 0x40) ? "Yes" : "No");

                if (readpos[0] & 0x4) {
                        printk(KERN_INFO "ide-tape: Block location is unknown"
                                         "to the tape\n");
                        clear_bit(IDETAPE_FLAG_ADDRESS_VALID, &tape->flags);
                        idetape_end_request(drive, 0, 0);
                } else {
                        debug_log(DBG_SENSE, "Block Location - %u\n",
                                        be32_to_cpu(*(u32 *)&readpos[4]));

                        tape->partition = readpos[1];
                        tape->first_frame =
                                be32_to_cpu(*(u32 *)&readpos[4]);
                        set_bit(IDETAPE_FLAG_ADDRESS_VALID, &tape->flags);
                        idetape_end_request(drive, 1, 0);
                }
        } else {
                idetape_end_request(drive, 0, 0);
        }
        return ide_stopped;
}

/*
 * Write a filemark if write_filemark=1. Flush the device buffers without
 * writing a filemark otherwise.
 */
static void idetape_create_write_filemark_cmd(ide_drive_t *drive,
                struct ide_atapi_pc *pc, int write_filemark)
{
        idetape_init_pc(pc);
        pc->c[0] = WRITE_FILEMARKS;
        pc->c[4] = write_filemark;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

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

/*
 * 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 on 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 ide_tape_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, struct ide_atapi_pc *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,
                struct ide_atapi_pc *pc, int cmd)
{
        idetape_init_pc(pc);
        pc->c[0] = START_STOP;
        pc->c[4] = cmd;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

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

        /* Wait for the tape to become ready */
        set_bit(IDETAPE_FLAG_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_flush_tape_buffers(ide_drive_t *drive)
{
        struct ide_atapi_pc pc;
        int rc;

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

static void idetape_create_read_position_cmd(struct ide_atapi_pc *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = READ_POSITION;
        pc->req_xfer = 20;
        pc->idetape_callback = &idetape_read_position_callback;
}

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

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

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

static void idetape_create_locate_cmd(ide_drive_t *drive,
                struct ide_atapi_pc *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;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

static int idetape_create_prevent_cmd(ide_drive_t *drive,
                struct ide_atapi_pc *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->idetape_callback = &idetape_pc_callback;
        return 1;
}

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

        if (tape->chrdev_dir != IDETAPE_DIR_READ)
                return;

        clear_bit(IDETAPE_FLAG_FILEMARK, &tape->flags);
        tape->merge_bh_size = 0;
        if (tape->merge_stage != NULL) {
                ide_tape_kfree_buffer(tape->merge_stage);
                tape->merge_stage = NULL;
        }

        tape->chrdev_dir = IDETAPE_DIR_NONE;
}

/*
 * Position 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;
        struct ide_atapi_pc pc;

        if (tape->chrdev_dir == IDETAPE_DIR_READ)
                __ide_tape_discard_merge_buffer(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 ide_tape_discard_merge_buffer(ide_drive_t *drive,
                                          int restore_position)
{
        idetape_tape_t *tape = drive->driver_data;
        int seek, position;

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

/*
 * Generate 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;

        debug_log(DBG_SENSE, "%s: cmd=%d\n", __func__, cmd);

        idetape_init_rq(&rq, cmd);
        rq.rq_disk = tape->disk;
        rq.special = (void *)bh;
        rq.sector = tape->first_frame;
        rq.nr_sectors           = blocks;
        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->blk_size * (blocks-rq.current_nr_sectors));
}

static void idetape_create_inquiry_cmd(struct ide_atapi_pc *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = INQUIRY;
        pc->c[4] = 254;
        pc->req_xfer = 254;
        pc->idetape_callback = &idetape_pc_callback;
}

static void idetape_create_rewind_cmd(ide_drive_t *drive,
                struct ide_atapi_pc *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = REZERO_UNIT;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

static void idetape_create_erase_cmd(struct ide_atapi_pc *pc)
{
        idetape_init_pc(pc);
        pc->c[0] = ERASE;
        pc->c[1] = 1;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

static void idetape_create_space_cmd(struct ide_atapi_pc *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;
        pc->flags |= PC_FLAG_WAIT_FOR_DSC;
        pc->idetape_callback = &idetape_pc_callback;
}

/* Queue up a character device originated write request. */
static int idetape_add_chrdev_write_request(ide_drive_t *drive, int blocks)
{
        idetape_tape_t *tape = drive->driver_data;

        debug_log(DBG_CHRDEV, "Enter %s\n", __func__);

        return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE,
                                     blocks, tape->merge_stage->bh);
}

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

        if (tape->chrdev_dir != IDETAPE_DIR_WRITE) {
                printk(KERN_ERR "ide-tape: bug: Trying to empty write pipeline,"
                                " but we are not writing.\n");
                return;
        }
        if (tape->merge_bh_size > tape->buffer_size) {
                printk(KERN_ERR "ide-tape: bug: merge_buffer too big\n");
                tape->merge_bh_size = tape->buffer_size;
        }
        if (tape->merge_bh_size) {
                blocks = tape->merge_bh_size / tape->blk_size;
                if (tape->merge_bh_size % tape->blk_size) {
                        unsigned int i;

                        blocks++;
                        i = tape->blk_size - tape->merge_bh_size %
                                tape->blk_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_bh_size = 0;
        }
        if (tape->merge_stage != NULL) {
                ide_tape_kfree_buffer(tape->merge_stage);
                tape->merge_stage = NULL;
        }
        tape->chrdev_dir = IDETAPE_DIR_NONE;
}

static int idetape_init_read(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        int bytes_read;

        /* Initialize read operation */
        if (tape->chrdev_dir != IDETAPE_DIR_READ) {
                if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
                        ide_tape_flush_merge_buffer(drive);
                        idetape_flush_tape_buffers(drive);
                }
                if (tape->merge_stage || tape->merge_bh_size) {
                        printk(KERN_ERR "ide-tape: merge_bh_size should be"
                                         " 0 now\n");
                        tape->merge_bh_size = 0;
                }
                tape->merge_stage = ide_tape_kmalloc_buffer(tape, 0, 0);
                if (!tape->merge_stage)
                        return -ENOMEM;
                tape->chrdev_dir = IDETAPE_DIR_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) {
                                ide_tape_kfree_buffer(tape->merge_stage);
                                tape->merge_stage = NULL;
                                tape->chrdev_dir = IDETAPE_DIR_NONE;
                                return bytes_read;
                        }
                }
        }

        return 0;
}

/* called from idetape_chrdev_read() to service a chrdev read request. */
static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
{
        idetape_tape_t *tape = drive->driver_data;

        debug_log(DBG_PROCS, "Enter %s, %d blocks\n", __func__, blocks);

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

        idetape_init_read(drive);

        return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks,
                                     tape->merge_stage->bh);
}

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->buffer_size, bcount);
                bcount -= count;
                blocks = count / tape->blk_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);
        }
}

/*
 * 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;
        struct ide_atapi_pc pc;
        idetape_tape_t *tape;
        tape = drive->driver_data;

        debug_log(DBG_SENSE, "Enter %s\n", __func__);

        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;
}

/* mtio.h compatible commands should be issued to the chrdev 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;

        debug_log(DBG_PROCS, "Enter %s\n", __func__);

        switch (cmd) {
        case 0x0340:
                if (copy_from_user(&config, argp, sizeof(config)))
                        return -EFAULT;
                tape->best_dsc_rw_freq = config.dsc_rw_frequency;
                break;
        case 0x0350:
                config.dsc_rw_frequency = (int) tape->best_dsc_rw_freq;
                config.nr_stages = 1;
                if (copy_to_user(argp, &config, sizeof(config)))
                        return -EFAULT;
                break;
        default:
                return -EIO;
        }
        return 0;
}

static int idetape_space_over_filemarks(ide_drive_t *drive, short mt_op,
                                        int mt_count)
{
        idetape_tape_t *tape = drive->driver_data;
        struct ide_atapi_pc pc;
        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_dir == IDETAPE_DIR_READ) {
                tape->merge_bh_size = 0;
                if (test_and_clear_bit(IDETAPE_FLAG_FILEMARK, &tape->flags))
                        ++count;
                ide_tape_discard_merge_buffer(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 (26kB on my particular tape, 32kB 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];

        debug_log(DBG_CHRDEV, "Enter %s, count %Zd\n", __func__, count);

        if (tape->chrdev_dir != IDETAPE_DIR_READ) {
                if (test_bit(IDETAPE_FLAG_DETECT_BS, &tape->flags))
                        if (count > tape->blk_size &&
                            (count % tape->blk_size) == 0)
                                tape->user_bs_factor = count / tape->blk_size;
        }
        rc = idetape_init_read(drive);
        if (rc < 0)
                return rc;
        if (count == 0)
                return (0);
        if (tape->merge_bh_size) {
                actually_read = min((unsigned int)(tape->merge_bh_size),
                                    (unsigned int)count);
                if (idetape_copy_stage_to_user(tape, buf, actually_read))
                        ret = -EFAULT;
                buf += actually_read;
                tape->merge_bh_size -= actually_read;
                count -= actually_read;
        }
        while (count >= tape->buffer_size) {
                bytes_read = idetape_add_chrdev_read_request(drive, ctl);
                if (bytes_read <= 0)
                        goto finish;
                if (idetape_copy_stage_to_user(tape, buf, 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, temp))
                        ret = -EFAULT;
                actually_read += temp;
                tape->merge_bh_size = bytes_read-temp;
        }
finish:
        if (!actually_read && test_bit(IDETAPE_FLAG_FILEMARK, &tape->flags)) {
                debug_log(DBG_SENSE, "%s: spacing over filemark\n", tape->name);

                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;

        debug_log(DBG_CHRDEV, "Enter %s, count %Zd\n", __func__, count);

        /* Initialize write operation */
        if (tape->chrdev_dir != IDETAPE_DIR_WRITE) {
                if (tape->chrdev_dir == IDETAPE_DIR_READ)
                        ide_tape_discard_merge_buffer(drive, 1);
                if (tape->merge_stage || tape->merge_bh_size) {
                        printk(KERN_ERR "ide-tape: merge_bh_size "
                                "should be 0 now\n");
                        tape->merge_bh_size = 0;
                }
                tape->merge_stage = ide_tape_kmalloc_buffer(tape, 0, 0);
                if (!tape->merge_stage)
                        return -ENOMEM;
                tape->chrdev_dir = IDETAPE_DIR_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) {
                                ide_tape_kfree_buffer(tape->merge_stage);
                                tape->merge_stage = NULL;
                                tape->chrdev_dir = IDETAPE_DIR_NONE;
                                return retval;
                        }
                }
        }
        if (count == 0)
                return (0);
        if (tape->merge_bh_size) {
                if (tape->merge_bh_size >= tape->buffer_size) {
                        printk(KERN_ERR "ide-tape: bug: merge buf too big\n");
                        tape->merge_bh_size = 0;
                }
                actually_written = min((unsigned int)
                                (tape->buffer_size - tape->merge_bh_size),
                                (unsigned int)count);
                if (idetape_copy_stage_from_user(tape, buf, actually_written))
                                ret = -EFAULT;
                buf += actually_written;
                tape->merge_bh_size += actually_written;
                count -= actually_written;

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

static int idetape_write_filemark(ide_drive_t *drive)
{
        struct ide_atapi_pc 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.
 *
 * 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;
        struct ide_atapi_pc pc;
        int i, retval;

        debug_log(DBG_ERR, "Handling MTIOCTOP ioctl: mt_op=%d, mt_count=%d\n",
                        mt_op, mt_count);

        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;
                ide_tape_discard_merge_buffer(drive, 1);
                for (i = 0; i < mt_count; i++) {
                        retval = idetape_write_filemark(drive);
                        if (retval)
                                return retval;
                }
                return 0;
        case MTREW:
                ide_tape_discard_merge_buffer(drive, 0);
                if (idetape_rewind_tape(drive))
                        return -EIO;
                return 0;
        case MTLOAD:
                ide_tape_discard_merge_buffer(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;
                }
                ide_tape_discard_merge_buffer(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_FLAG_MEDIUM_PRESENT, &tape->flags);
                return retval;
        case MTNOP:
                ide_tape_discard_merge_buffer(drive, 0);
                return idetape_flush_tape_buffers(drive);
        case MTRETEN:
                ide_tape_discard_merge_buffer(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->blk_size ||
                            mt_count % tape->blk_size)
                                return -EIO;
                        tape->user_bs_factor = mt_count / tape->blk_size;
                        clear_bit(IDETAPE_FLAG_DETECT_BS, &tape->flags);
                } else
                        set_bit(IDETAPE_FLAG_DETECT_BS, &tape->flags);
                return 0;
        case MTSEEK:
                ide_tape_discard_merge_buffer(drive, 0);
                return idetape_position_tape(drive,
                        mt_count * tape->user_bs_factor, tape->partition, 0);
        case MTSETPART:
                ide_tape_discard_merge_buffer(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;
        void __user *argp = (void __user *)arg;

        debug_log(DBG_CHRDEV, "Enter %s, cmd=%u\n", __func__, cmd);

        if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
                ide_tape_flush_merge_buffer(drive);
                idetape_flush_tape_buffers(drive);
        }
        if (cmd == MTIOCGET || cmd == MTIOCPOS) {
                block_offset = tape->merge_bh_size /
                        (tape->blk_size * tape->user_bs_factor);
                position = idetape_read_position(drive);
                if (position < 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->blk_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_dir == IDETAPE_DIR_READ)
                        ide_tape_discard_merge_buffer(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;
        struct ide_atapi_pc 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->blk_size == 0) {
                        printk(KERN_WARNING "ide-tape: Cannot deal with zero "
                                            "block size, assuming 32k\n");
                        tape->blk_size = 32768;
                }
                return;
        }
        tape->blk_size = (pc.buf[4 + 5] << 16) +
                                (pc.buf[4 + 6] << 8)  +
                                 pc.buf[4 + 7];
        tape->drv_write_prot = (pc.buf[2] & 0x80) >> 7;
}

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;
        struct ide_atapi_pc pc;
        int retval;

        if (i >= MAX_HWIFS * MAX_DRIVES)
                return -ENXIO;

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

        debug_log(DBG_CHRDEV, "Enter %s\n", __func__);

        /*
         * 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);

        drive = tape->drive;

        filp->private_data = tape;

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

        retval = idetape_wait_ready(drive, 60 * HZ);
        if (retval) {
                clear_bit(IDETAPE_FLAG_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_FLAG_ADDRESS_VALID, &tape->flags))
                (void)idetape_rewind_tape(drive);

        /* 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_FLAG_BUSY, &tape->flags);
                        retval = -EROFS;
                        goto out_put_tape;
                }
        }

        /* Lock the tape drive door so user can't eject. */
        if (tape->chrdev_dir == IDETAPE_DIR_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;
                        }
                }
        }
        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;

        ide_tape_flush_merge_buffer(drive);
        tape->merge_stage = ide_tape_kmalloc_buffer(tape, 1, 0);
        if (tape->merge_stage != NULL) {
                idetape_pad_zeros(drive, tape->blk_size *
                                (tape->user_bs_factor - 1));
                ide_tape_kfree_buffer(tape->merge_stage);
                tape->merge_stage = NULL;
        }
        idetape_write_filemark(drive);
        idetape_flush_tape_buffers(drive);
        idetape_flush_tape_buffers(drive);
}

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;
        struct ide_atapi_pc pc;
        unsigned int minor = iminor(inode);

        lock_kernel();
        tape = drive->driver_data;

        debug_log(DBG_CHRDEV, "Enter %s\n", __func__);

        if (tape->chrdev_dir == IDETAPE_DIR_WRITE)
                idetape_write_release(drive, minor);
        if (tape->chrdev_dir == IDETAPE_DIR_READ) {
                if (minor < 128)
                        ide_tape_discard_merge_buffer(drive, 1);
        }

        if (minor < 128 && test_bit(IDETAPE_FLAG_MEDIUM_PRESENT, &tape->flags))
                (void) idetape_rewind_tape(drive);
        if (tape->chrdev_dir == IDETAPE_DIR_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_FLAG_BUSY, &tape->flags);
        ide_tape_put(tape);
        unlock_kernel();
        return 0;
}

/*
 * 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)
{
        u8 gcw[2], protocol, device_type, removable, packet_size;

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

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

        protocol        =   (gcw[1] & 0xC0) >> 6;
        device_type     =    gcw[1] & 0x1F;
        removable       = !!(gcw[0] & 0x80);
        packet_size     =    gcw[0] & 0x3;

        /* Check that we can support this device */
        if (protocol != 2)
                printk(KERN_ERR "ide-tape: Protocol (0x%02x) is not ATAPI\n",
                                protocol);
        else if (device_type != 1)
                printk(KERN_ERR "ide-tape: Device type (0x%02x) is not set "
                                "to tape\n", device_type);
        else if (!removable)
                printk(KERN_ERR "ide-tape: The removable flag is not set\n");
        else if (packet_size != 0) {
                printk(KERN_ERR "ide-tape: Packet size (0x%02x) is not 12"
                                " bytes\n", packet_size);
        } else
                return 1;
        return 0;
}

static void idetape_get_inquiry_results(ide_drive_t *drive)
{
        idetape_tape_t *tape = drive->driver_data;
        struct ide_atapi_pc pc;
        char fw_rev[6], vendor_id[10], product_id[18];

        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(vendor_id, &pc.buf[8], 8);
        memcpy(product_id, &pc.buf[16], 16);
        memcpy(fw_rev, &pc.buf[32], 4);

        ide_fixstring(vendor_id, 10, 0);
        ide_fixstring(product_id, 18, 0);
        ide_fixstring(fw_rev, 6, 0);

        printk(KERN_INFO "ide-tape: %s <-> %s: %s %s rev %s\n",
                        drive->name, tape->name, vendor_id, product_id, fw_rev);
}

/*
 * 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;
        struct ide_atapi_pc 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->blk_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.buf + 4 + pc.buf[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->blk_size = 512;
        else if (caps[7] & 0x04)
                tape->blk_size = 1024;
}

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

        ide_add_setting(drive, "buffer", SETTING_READ, TYPE_SHORT, 0, 0xffff,
                        1, 2, (u16 *)&tape->caps[16], NULL);
        ide_add_setting(drive, "speed", SETTING_READ, TYPE_SHORT, 0, 0xffff,
                        1, 1, (u16 *)&tape->caps[14], NULL);
        ide_add_setting(drive, "buffer_size", SETTING_READ, TYPE_INT, 0, 0xffff,
                        1, 1024, &tape->buffer_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_freq,
                        NULL);
        ide_add_setting(drive, "dsc_overlap", SETTING_RW, TYPE_BYTE, 0, 1, 1,
                        1, &drive->dsc_overlap, NULL);
        ide_add_setting(drive, "avg_speed", SETTING_READ, TYPE_INT, 0, 0xffff,
                        1, 1, &tape->avg_speed, NULL);
        ide_add_setting(drive, "debug_mask", SETTING_RW, TYPE_INT, 0, 0xffff, 1,
                        1, &tape->debug_mask, NULL);
}
#else
static inline void idetape_add_settings(ide_drive_t *drive) { ; }
#endif

/*
 * The function below 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 t;
        int speed;
        int buffer_size;
        u8 gcw[2];
        u16 *ctl = (u16 *)&tape->caps[12];

        spin_lock_init(&tape->lock);
        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_dir = IDETAPE_DIR_NONE;
        tape->pc = tape->pc_stack;
        *((unsigned short *) &gcw) = drive->id->config;

        /* Command packet DRQ type */
        if (((gcw[0] & 0x60) >> 5) == 1)
                set_bit(IDETAPE_FLAG_DRQ_INTERRUPT, &tape->flags);

        idetape_get_inquiry_results(drive);
        idetape_get_mode_sense_results(drive);
        ide_tape_get_bsize_from_bdesc(drive);
        tape->user_bs_factor = 1;
        tape->buffer_size = *ctl * tape->blk_size;
        while (tape->buffer_size > 0xffff) {
                printk(KERN_NOTICE "ide-tape: decreasing stage size\n");
                *ctl /= 2;
                tape->buffer_size = *ctl * tape->blk_size;
        }
        buffer_size = tape->buffer_size;
        tape->pages_per_buffer = buffer_size / PAGE_SIZE;
        if (buffer_size % PAGE_SIZE) {
                tape->pages_per_buffer++;
                tape->excess_bh_size = PAGE_SIZE - buffer_size % PAGE_SIZE;
        }

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

        t = (IDETAPE_FIFO_THRESHOLD * tape->buffer_size * HZ) / (speed * 1000);

        /*
         * Ensure that the number we got makes sense; limit it within
         * IDETAPE_DSC_RW_MIN and IDETAPE_DSC_RW_MAX.
         */
        tape->best_dsc_rw_freq = 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, "
                "%lums tDSC%s\n",
                drive->name, tape->name, *(u16 *)&tape->caps[14],
                (*(u16 *)&tape->caps[16] * 512) / tape->buffer_size,
                tape->buffer_size / 1024,
                tape->best_dsc_rw_freq * 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->merge_bh_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;

        tape = ide_tape_get(disk);
        if (!tape)
                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"
                                " the driver\n", drive->name);
                goto failed;
        }
        if (drive->scsi) {
                printk(KERN_INFO "ide-tape: passing drive %s to ide-scsi"
                                 " emulation.\n", drive->name);
                goto failed;
        }
        tape = kzalloc(sizeof(idetape_tape_t), GFP_KERNEL);
        if (tape == NULL) {
                printk(KERN_ERR "ide-tape: %s: Can't allocate a tape struct\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;
}

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