/*

   * 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 DRV_NAME "ide-tape"

  #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/seq_file.h>

  #include <linux/slab.h>
  #include <linux/pci.h>
  #include <linux/ide.h>

  #include <linux/completion.h>
  #include <linux/bitops.h>

  #include <linux/mutex.h>

  #include <scsi/scsi.h>

  
  #include <asm/byteorder.h>

  #include <linux/uaccess.h>
  #include <linux/io.h>

  #include <asm/unaligned.h>

  #include <linux/mtio.h>

  /* define to see debug info */

  #undef IDETAPE_DEBUG_LOG

  #ifdef IDETAPE_DEBUG_LOG
  #define ide_debug_log(lvl, fmt, args...) __ide_debug_log(lvl, fmt, ## args)

  #else

  #define ide_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
  
  /*

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

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

  /* 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

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

  /*

   * 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;
  	struct ide_driver	*driver;
  	struct gendisk		*disk;

  	struct device		dev;

  	/* used by REQ_IDETAPE_{READ,WRITE} requests */
  	struct ide_atapi_pc queued_pc;

  	/*

  	 * 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.

  	 */

  	bool 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;

  	/* Staging buffer of buffer_size bytes */
  	void *buf;
  	/* The read/write cursor */
  	void *cur;
  	/* The number of valid bytes in buf */
  	size_t valid;

  	/* 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;

  } idetape_tape_t;

  static DEFINE_MUTEX(ide_tape_mutex);

  static DEFINE_MUTEX(idetape_ref_mutex);

  static DEFINE_MUTEX(idetape_chrdev_mutex);

  static struct class *idetape_sysfs_class;

  static void ide_tape_release(struct device *);

  static struct ide_tape_obj *idetape_devs[MAX_HWIFS * MAX_DRIVES];
  
  static struct ide_tape_obj *ide_tape_get(struct gendisk *disk, bool cdev,
  					 unsigned int i)

  {
  	struct ide_tape_obj *tape = NULL;

  	mutex_lock(&idetape_ref_mutex);

  
  	if (cdev)
  		tape = idetape_devs[i];
  	else
  		tape = ide_drv_g(disk, ide_tape_obj);

  	if (tape) {

  		if (ide_device_get(tape->drive))

  			tape = NULL;

  		else

  			get_device(&tape->dev);

  	}

  	mutex_unlock(&idetape_ref_mutex);

  	return tape;
  }

  static void ide_tape_put(struct ide_tape_obj *tape)
  {

  	ide_drive_t *drive = tape->drive;

  	mutex_lock(&idetape_ref_mutex);

  	put_device(&tape->dev);

  	ide_device_put(drive);

  	mutex_unlock(&idetape_ref_mutex);

  }

  /*

   * called on each failed packet command retry to analyze the request sense. We
   * currently do not utilize this information.

   */

  static void idetape_analyze_error(ide_drive_t *drive)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	struct ide_atapi_pc *pc = drive->failed_pc;

  	struct request *rq = drive->hwif->rq;

  	u8 *sense = bio_data(rq->bio);

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

  	ide_debug_log(IDE_DBG_FUNC,
  		      "cmd: 0x%x, sense key = %x, asc = %x, ascq = %x",
  		      rq->cmd[0], tape->sense_key, tape->asc, tape->ascq);

  	/* correct remaining bytes to transfer */

  	if (pc->flags & PC_FLAG_DMA_ERROR)

  		rq->resid_len = tape->blk_size * get_unaligned_be32(&sense[3]);

  
  	/*
  	 * 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 = IDE_DRV_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 = IDE_DRV_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 = IDE_DRV_ERROR_EOD;

  			pc->flags |= PC_FLAG_ABORT;

  		}

  		if (!(pc->flags & PC_FLAG_ABORT) &&

  		    (blk_rq_bytes(rq) - rq->resid_len))

  			pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
  	}
  }

  static void ide_tape_handle_dsc(ide_drive_t *);

  static int ide_tape_callback(ide_drive_t *drive, int dsc)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	struct ide_atapi_pc *pc = drive->pc;

  	struct request *rq = drive->hwif->rq;

  	int uptodate = pc->error ? 0 : 1;

  	int err = uptodate ? 0 : IDE_DRV_ERROR_GENERAL;

  	ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, dsc: %d, err: %d", rq->cmd[0],
  		      dsc, err);

  	if (dsc)
  		ide_tape_handle_dsc(drive);

  	if (drive->failed_pc == pc)
  		drive->failed_pc = NULL;

  	if (pc->c[0] == REQUEST_SENSE) {
  		if (uptodate)

  			idetape_analyze_error(drive);

  		else
  			printk(KERN_ERR "ide-tape: Error in REQUEST SENSE "
  					"itself - Aborting request!
  ");
  	} else if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {

  		unsigned int blocks =
  			(blk_rq_bytes(rq) - rq->resid_len) / 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;
  		}
  
  		tape->first_frame += blocks;

  		if (pc->error) {
  			uptodate = 0;
  			err = pc->error;
  		}

  	}

  	rq->errors = err;

  	return uptodate;

  }

  /*

   * Postpone the current request so that ide.c will be able to service requests

   * from another device on the same port while we are polling for DSC.

   */

  static void ide_tape_stall_queue(ide_drive_t *drive)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, dsc_poll_freq: %lu",

  		      drive->hwif->rq->cmd[0], tape->dsc_poll_freq);

  	tape->postponed_rq = true;

  	ide_stall_queue(drive, tape->dsc_poll_freq);

  }

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

  	ide_tape_stall_queue(drive);

  }

  /*

   * Packet Command Interface

   *

   * The current Packet Command is available in drive->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. ide_tape_issue_pc will send the packet command to the drive, and will set

   * the interrupt handler to ide_pc_intr.

   *

   * 2. On each interrupt, ide_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 ide_tape_issue_pc(ide_drive_t *drive,
  					 struct ide_cmd *cmd,
  					 struct ide_atapi_pc *pc)

  {

  	idetape_tape_t *tape = drive->driver_data;

  	struct request *rq = drive->hwif->rq;

  	if (drive->failed_pc == NULL && pc->c[0] != REQUEST_SENSE)
  		drive->failed_pc = pc;

  	/* Set the current packet command */

  	drive->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
  ",
  						tape->name, pc->c[0],
  						tape->sense_key, tape->asc,
  						tape->ascq);
  			}
  			/* Giving up */

  			pc->error = IDE_DRV_ERROR_GENERAL;

  		}

  		drive->failed_pc = NULL;

  		drive->pc_callback(drive, 0);

  		ide_complete_rq(drive, -EIO, blk_rq_bytes(rq));

  		return ide_stopped;

  	}

  	ide_debug_log(IDE_DBG_SENSE, "retry #%d, cmd: 0x%02x", pc->retries,
  		      pc->c[0]);

  
  	pc->retries++;

  	return ide_issue_pc(drive, cmd);

  }

  /* 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)

  {

  	ide_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;

  }

  static ide_startstop_t idetape_media_access_finished(ide_drive_t *drive)

  {

  	ide_hwif_t *hwif = drive->hwif;

  	idetape_tape_t *tape = drive->driver_data;

  	struct ide_atapi_pc *pc = drive->pc;

  	u8 stat;

  	stat = hwif->tp_ops->read_status(hwif);

  	if (stat & ATA_DSC) {
  		if (stat & ATA_ERR) {

  			/* Error detected */

  			if (pc->c[0] != TEST_UNIT_READY)

  				printk(KERN_ERR "ide-tape: %s: I/O error, ",
  						tape->name);
  			/* Retry operation */

  			ide_retry_pc(drive);

  			return ide_stopped;

  		}
  		pc->error = 0;

  	} else {

  		pc->error = IDE_DRV_ERROR_GENERAL;

  		drive->failed_pc = NULL;

  	}

  	drive->pc_callback(drive, 0);

  	return ide_stopped;
  }

  static void ide_tape_create_rw_cmd(idetape_tape_t *tape,

  				   struct ide_atapi_pc *pc, struct request *rq,
  				   u8 opcode)

  {

  	unsigned int length = blk_rq_sectors(rq) / (tape->blk_size >> 9);

  	ide_init_pc(pc);

  	put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);

  	pc->c[1] = 1;

  
  	if (blk_rq_bytes(rq) == tape->buffer_size)

  		pc->flags |= PC_FLAG_DMA_OK;

  	if (opcode == READ_6)

  		pc->c[0] = READ_6;

  	else if (opcode == WRITE_6) {

  		pc->c[0] = WRITE_6;
  		pc->flags |= PC_FLAG_WRITING;

  	}

  
  	memcpy(rq->cmd, pc->c, 12);

  }

  static ide_startstop_t idetape_do_request(ide_drive_t *drive,
  					  struct request *rq, sector_t block)
  {

  	ide_hwif_t *hwif = drive->hwif;

  	idetape_tape_t *tape = drive->driver_data;

  	struct ide_atapi_pc *pc = NULL;

  	struct ide_cmd cmd;

  	u8 stat;

  	ide_debug_log(IDE_DBG_RQ, "cmd: 0x%x, sector: %llu, nr_sectors: %u",
  		      rq->cmd[0], (unsigned long long)blk_rq_pos(rq),
  		      blk_rq_sectors(rq));

  	BUG_ON(!(rq->cmd_type == REQ_TYPE_SPECIAL ||
  		 rq->cmd_type == REQ_TYPE_SENSE));

  	/* Retry a failed packet command */

  	if (drive->failed_pc && drive->pc->c[0] == REQUEST_SENSE) {
  		pc = drive->failed_pc;

  		goto out;
  	}

  	/*
  	 * If the tape is still busy, postpone our request and service
  	 * the other device meanwhile.
  	 */

  	stat = hwif->tp_ops->read_status(hwif);

  	if ((drive->dev_flags & IDE_DFLAG_DSC_OVERLAP) == 0 &&
  	    (rq->cmd[13] & REQ_IDETAPE_PC2) == 0)

  		drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;

  	if (drive->dev_flags & IDE_DFLAG_POST_RESET) {

  		drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;

  		drive->dev_flags &= ~IDE_DFLAG_POST_RESET;

  	}

  	if (!(drive->atapi_flags & IDE_AFLAG_IGNORE_DSC) &&
  	    !(stat & ATA_DSC)) {

  		if (!tape->postponed_rq) {

  			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
  ",
  				tape->name);

  			if (rq->cmd[13] & 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;

  		ide_tape_stall_queue(drive);

  		return ide_stopped;

  	} else {

  		drive->atapi_flags &= ~IDE_AFLAG_IGNORE_DSC;

  		tape->postponed_rq = false;
  	}

  	if (rq->cmd[13] & REQ_IDETAPE_READ) {

  		pc = &tape->queued_pc;

  		ide_tape_create_rw_cmd(tape, pc, rq, READ_6);

  		goto out;
  	}

  	if (rq->cmd[13] & REQ_IDETAPE_WRITE) {

  		pc = &tape->queued_pc;

  		ide_tape_create_rw_cmd(tape, pc, rq, WRITE_6);

  		goto out;
  	}

  	if (rq->cmd[13] & REQ_IDETAPE_PC1) {

  		pc = (struct ide_atapi_pc *)rq->special;

  		rq->cmd[13] &= ~(REQ_IDETAPE_PC1);
  		rq->cmd[13] |= REQ_IDETAPE_PC2;

  		goto out;
  	}

  	if (rq->cmd[13] & REQ_IDETAPE_PC2) {

  		idetape_media_access_finished(drive);
  		return ide_stopped;
  	}
  	BUG();

  out:

  	/* prepare sense request for this command */
  	ide_prep_sense(drive, rq);

  	memset(&cmd, 0, sizeof(cmd));
  
  	if (rq_data_dir(rq))
  		cmd.tf_flags |= IDE_TFLAG_WRITE;
  
  	cmd.rq = rq;

  	ide_init_sg_cmd(&cmd, blk_rq_bytes(rq));

  	ide_map_sg(drive, &cmd);

  	return ide_tape_issue_pc(drive, &cmd, pc);

  }

  /*

   * 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)

  {

  	ide_init_pc(pc);

  	pc->c[0] = WRITE_FILEMARKS;

  	pc->c[4] = write_filemark;

  	pc->flags |= PC_FLAG_WAIT_FOR_DSC;

  }

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

  	struct gendisk *disk = tape->disk;

  	int load_attempted = 0;

  	/* Wait for the tape to become ready */

  	set_bit(ilog2(IDE_AFLAG_MEDIUM_PRESENT), &drive->atapi_flags);

  	timeout += jiffies;
  	while (time_before(jiffies, timeout)) {

  		if (ide_do_test_unit_ready(drive, disk) == 0)

  			return 0;
  		if ((tape->sense_key == 2 && tape->asc == 4 && tape->ascq == 2)

  		    || (tape->asc == 0x3A)) {
  			/* no media */

  			if (load_attempted)
  				return -ENOMEDIUM;

  			ide_do_start_stop(drive, disk, IDETAPE_LU_LOAD_MASK);

  			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_tape_obj *tape = drive->driver_data;

  	struct ide_atapi_pc pc;

  	int rc;
  
  	idetape_create_write_filemark_cmd(drive, &pc, 0);

  	rc = ide_queue_pc_tail(drive, tape->disk, &pc, NULL, 0);

  	if (rc)

  		return rc;
  	idetape_wait_ready(drive, 60 * 5 * HZ);
  	return 0;
  }

  static int ide_tape_read_position(ide_drive_t *drive)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	struct ide_atapi_pc pc;

  	u8 buf[20];

  	ide_debug_log(IDE_DBG_FUNC, "enter");

  	/* prep cmd */
  	ide_init_pc(&pc);
  	pc.c[0] = READ_POSITION;
  	pc.req_xfer = 20;
  
  	if (ide_queue_pc_tail(drive, tape->disk, &pc, buf, pc.req_xfer))

  		return -1;

  
  	if (!pc.error) {

  		ide_debug_log(IDE_DBG_FUNC, "BOP - %s",

  				(buf[0] & 0x80) ? "Yes" : "No");

  		ide_debug_log(IDE_DBG_FUNC, "EOP - %s",

  				(buf[0] & 0x40) ? "Yes" : "No");
  
  		if (buf[0] & 0x4) {
  			printk(KERN_INFO "ide-tape: Block location is unknown"
  					 "to the tape
  ");

  			clear_bit(ilog2(IDE_AFLAG_ADDRESS_VALID),
  				  &drive->atapi_flags);

  			return -1;
  		} else {

  			ide_debug_log(IDE_DBG_FUNC, "Block Location: %u",
  				      be32_to_cpup((__be32 *)&buf[4]));

  
  			tape->partition = buf[1];
  			tape->first_frame = be32_to_cpup((__be32 *)&buf[4]);

  			set_bit(ilog2(IDE_AFLAG_ADDRESS_VALID),
  				&drive->atapi_flags);

  		}
  	}
  
  	return tape->first_frame;

  }

  static void idetape_create_locate_cmd(ide_drive_t *drive,
  		struct ide_atapi_pc *pc,

  		unsigned int block, u8 partition, int skip)

  {

  	ide_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;

  }

  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(ilog2(IDE_AFLAG_FILEMARK), &drive->atapi_flags);

  	tape->valid = 0;
  	if (tape->buf != NULL) {
  		kfree(tape->buf);
  		tape->buf = 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;

  	struct gendisk *disk = tape->disk;

  	int ret;

  	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);

  	ret = ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
  	if (ret)
  		return ret;

  	ret = ide_tape_read_position(drive);
  	if (ret < 0)
  		return ret;
  	return 0;

  }

  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 = ide_tape_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
  ", 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 size)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	struct request *rq;

  	int ret;

  	ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%x, size: %d", cmd, size);

  	BUG_ON(cmd != REQ_IDETAPE_READ && cmd != REQ_IDETAPE_WRITE);

  	BUG_ON(size < 0 || size % tape->blk_size);

  	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
  	rq->cmd_type = REQ_TYPE_SPECIAL;

  	rq->cmd[13] = cmd;

  	rq->rq_disk = tape->disk;

  	rq->__sector = tape->first_frame;

  
  	if (size) {

  		ret = blk_rq_map_kern(drive->queue, rq, tape->buf, size,

  				      __GFP_WAIT);
  		if (ret)
  			goto out_put;
  	}

  	blk_execute_rq(drive->queue, tape->disk, rq, 0);

  	/* calculate the number of transferred bytes and update buffer state */

  	size -= rq->resid_len;

  	tape->cur = tape->buf;

  	if (cmd == REQ_IDETAPE_READ)

  		tape->valid = size;
  	else
  		tape->valid = 0;

  	ret = size;
  	if (rq->errors == IDE_DRV_ERROR_GENERAL)
  		ret = -EIO;

  out_put:
  	blk_put_request(rq);

  	return ret;

  }

  static void idetape_create_inquiry_cmd(struct ide_atapi_pc *pc)

  {

  	ide_init_pc(pc);

  	pc->c[0] = INQUIRY;

  	pc->c[4] = 254;

  	pc->req_xfer = 254;

  }

  static void idetape_create_rewind_cmd(ide_drive_t *drive,
  		struct ide_atapi_pc *pc)

  {

  	ide_init_pc(pc);

  	pc->c[0] = REZERO_UNIT;

  	pc->flags |= PC_FLAG_WAIT_FOR_DSC;

  }

  static void idetape_create_erase_cmd(struct ide_atapi_pc *pc)

  {

  	ide_init_pc(pc);

  	pc->c[0] = ERASE;

  	pc->c[1] = 1;

  	pc->flags |= PC_FLAG_WAIT_FOR_DSC;

  }

  static void idetape_create_space_cmd(struct ide_atapi_pc *pc, int count, u8 cmd)

  {

  	ide_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;

  }

  static void ide_tape_flush_merge_buffer(ide_drive_t *drive)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	if (tape->chrdev_dir != IDETAPE_DIR_WRITE) {

  		printk(KERN_ERR "ide-tape: bug: Trying to empty merge buffer"

  				" but we are not writing.
  ");

  		return;
  	}

  	if (tape->buf) {

  		size_t aligned = roundup(tape->valid, tape->blk_size);
  
  		memset(tape->cur, 0, aligned - tape->valid);

  		idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, aligned);

  		kfree(tape->buf);
  		tape->buf = NULL;

  	}

  	tape->chrdev_dir = IDETAPE_DIR_NONE;

  }

  static int idetape_init_rw(ide_drive_t *drive, int dir)

  {
  	idetape_tape_t *tape = drive->driver_data;

  	int rc;

  	BUG_ON(dir != IDETAPE_DIR_READ && dir != IDETAPE_DIR_WRITE);

  	if (tape->chrdev_dir == dir)
  		return 0;
  
  	if (tape->chrdev_dir == IDETAPE_DIR_READ)
  		ide_tape_discard_merge_buffer(drive, 1);
  	else if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
  		ide_tape_flush_merge_buffer(drive);
  		idetape_flush_tape_buffers(drive);
  	}
  
  	if (tape->buf || tape->valid) {
  		printk(KERN_ERR "ide-tape: valid should be 0 now
  ");
  		tape->valid = 0;
  	}
  
  	tape->buf = kmalloc(tape->buffer_size, GFP_KERNEL);
  	if (!tape->buf)
  		return -ENOMEM;
  	tape->chrdev_dir = dir;
  	tape->cur = tape->buf;
  
  	/*
  	 * Issue a 0 rw 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->dev_flags & IDE_DFLAG_DSC_OVERLAP) {
  		int cmd = dir == IDETAPE_DIR_READ ? REQ_IDETAPE_READ
  						  : REQ_IDETAPE_WRITE;
  
  		rc = idetape_queue_rw_tail(drive, cmd, 0);
  		if (rc < 0) {
  			kfree(tape->buf);
  			tape->buf = NULL;
  			tape->chrdev_dir = IDETAPE_DIR_NONE;
  			return rc;

  		}
  	}

  	return 0;
  }

  static void idetape_pad_zeros(ide_drive_t *drive, int bcount)

  {
  	idetape_tape_t *tape = drive->driver_data;

  
  	memset(tape->buf, 0, tape->buffer_size);

  	while (bcount) {

  		unsigned int count = min(tape->buffer_size, bcount);

  		idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, count);

  		bcount -= count;

  	}
  }

  /*

   * 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)

  {

  	struct ide_tape_obj *tape = drive->driver_data;
  	struct gendisk *disk = tape->disk;

  	struct ide_atapi_pc pc;

  	int ret;

  	ide_debug_log(IDE_DBG_FUNC, "enter");

  	idetape_create_rewind_cmd(drive, &pc);

  	ret = ide_queue_pc_tail(drive, disk, &pc, NULL, 0);
  	if (ret)
  		return ret;

  	ret = ide_tape_read_position(drive);
  	if (ret < 0)
  		return ret;

  	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;

  	ide_debug_log(IDE_DBG_FUNC, "cmd: 0x%04x", cmd);

  	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:

  		memset(&config, 0, sizeof(config));

  		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 gendisk *disk = tape->disk;

  	struct ide_atapi_pc pc;

  	int retval, count = 0;

  	int sprev = !!(tape->caps[4] & 0x20);

  
  	ide_debug_log(IDE_DBG_FUNC, "mt_op: %d, mt_count: %d", mt_op, mt_count);

  	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->valid = 0;

  		if (test_and_clear_bit(ilog2(IDE_AFLAG_FILEMARK),
  				       &drive->atapi_flags))

  			++count;

  		ide_tape_discard_merge_buffer(drive, 0);

  	}

  	switch (mt_op) {

  	case MTFSF:
  	case MTBSF:
  		idetape_create_space_cmd(&pc, mt_count - count,
  					 IDETAPE_SPACE_OVER_FILEMARK);

  		return ide_queue_pc_tail(drive, disk, &pc, NULL, 0);

  	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
  ",
  				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 = file->private_data;

  	ide_drive_t *drive = tape->drive;

  	size_t done = 0;

  	ssize_t ret = 0;

  	int rc;

  	ide_debug_log(IDE_DBG_FUNC, "count %Zd", count);

  	if (tape->chrdev_dir != IDETAPE_DIR_READ) {

  		if (test_bit(ilog2(IDE_AFLAG_DETECT_BS), &drive->atapi_flags))

  			if (count > tape->blk_size &&
  			    (count % tape->blk_size) == 0)
  				tape->user_bs_factor = count / tape->blk_size;

  	}

  	rc = idetape_init_rw(drive, IDETAPE_DIR_READ);

  	if (rc < 0)

  		return rc;

  
  	while (done < count) {
  		size_t todo;
  
  		/* refill if staging buffer is empty */
  		if (!tape->valid) {
  			/* If we are at a filemark, nothing more to read */

  			if (test_bit(ilog2(IDE_AFLAG_FILEMARK),
  				     &drive->atapi_flags))

  				break;
  			/* read */
  			if (idetape_queue_rw_tail(drive, REQ_IDETAPE_READ,
  						  tape->buffer_size) <= 0)
  				break;
  		}
  
  		/* copy out */
  		todo = min_t(size_t, count - done, tape->valid);
  		if (copy_to_user(buf + done, tape->cur, todo))

  			ret = -EFAULT;

  
  		tape->cur += todo;
  		tape->valid -= todo;
  		done += todo;

  	}