drivers/ide/ide-atapi.c - third_party/linux - Git at Google

 /*
  * ATAPI support.
  */

 #include <linux/kernel.h>
 #include <linux/cdrom.h>
 #include <linux/delay.h>
 #include <linux/export.h>
 #include <linux/ide.h>
 #include <linux/scatterlist.h>
 #include <linux/gfp.h>

 #include <scsi/scsi.h>

 #define DRV_NAME "ide-atapi"
 #define PFX DRV_NAME ": "

 #ifdef DEBUG
 #define debug_log(fmt, args...) \
 	printk(KERN_INFO "ide: " fmt, ## args)
 #else
 #define debug_log(fmt, args...) do {} while (0)
 #endif

 #define ATAPI_MIN_CDB_BYTES	12

 static inline int dev_is_idecd(ide_drive_t *drive)
 {
 	return drive->media == ide_cdrom || drive->media == ide_optical;
 }

 /*
  * Check whether we can support a device,
  * based on the ATAPI IDENTIFY command results.
  */
 int ide_check_atapi_device(ide_drive_t *drive, const char *s)
 {
 	u16 *id = drive->id;
 	u8 gcw[2], protocol, device_type, removable, drq_type, packet_size;

 	*((u16 *)&gcw) = id[ATA_ID_CONFIG];

 	protocol    = (gcw[1] & 0xC0) >> 6;
 	device_type =  gcw[1] & 0x1F;
 	removable   = (gcw[0] & 0x80) >> 7;
 	drq_type    = (gcw[0] & 0x60) >> 5;
 	packet_size =  gcw[0] & 0x03;

 #ifdef CONFIG_PPC
 	/* kludge for Apple PowerBook internal zip */
 	if (drive->media == ide_floppy && device_type == 5 &&
 	    !strstr((char *)&id[ATA_ID_PROD], "CD-ROM") &&
 	    strstr((char *)&id[ATA_ID_PROD], "ZIP"))
 		device_type = 0;
 #endif

 	if (protocol != 2)
 		printk(KERN_ERR "%s: %s: protocol (0x%02x) is not ATAPI\n",
 			s, drive->name, protocol);
 	else if ((drive->media == ide_floppy && device_type != 0) ||
 		 (drive->media == ide_tape && device_type != 1))
 		printk(KERN_ERR "%s: %s: invalid device type (0x%02x)\n",
 			s, drive->name, device_type);
 	else if (removable == 0)
 		printk(KERN_ERR "%s: %s: the removable flag is not set\n",
 			s, drive->name);
 	else if (drive->media == ide_floppy && drq_type == 3)
 		printk(KERN_ERR "%s: %s: sorry, DRQ type (0x%02x) not "
 			"supported\n", s, drive->name, drq_type);
 	else if (packet_size != 0)
 		printk(KERN_ERR "%s: %s: packet size (0x%02x) is not 12 "
 			"bytes\n", s, drive->name, packet_size);
 	else
 		return 1;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ide_check_atapi_device);

 void ide_init_pc(struct ide_atapi_pc *pc)
 {
 	memset(pc, 0, sizeof(*pc));
 }
 EXPORT_SYMBOL_GPL(ide_init_pc);

 /*
  * Add a special packet command request to the tail of the request queue,
  * and wait for it to be serviced.
  */
 int ide_queue_pc_tail(ide_drive_t *drive, struct gendisk *disk,
 		      struct ide_atapi_pc *pc, void *buf, unsigned int bufflen)
 {
 	struct request *rq;
 	int error;

 	rq = blk_get_request(drive->queue, READ, __GFP_RECLAIM);
 	scsi_req_init(rq);
 	rq->cmd_type = REQ_TYPE_DRV_PRIV;
 	rq->special = (char *)pc;

 	if (buf && bufflen) {
 		error = blk_rq_map_kern(drive->queue, rq, buf, bufflen,
 					GFP_NOIO);
 		if (error)
 			goto put_req;
 	}

 	memcpy(scsi_req(rq)->cmd, pc->c, 12);
 	if (drive->media == ide_tape)
 		scsi_req(rq)->cmd[13] = REQ_IDETAPE_PC1;
 	error = blk_execute_rq(drive->queue, disk, rq, 0);
 put_req:
 	blk_put_request(rq);
 	return error;
 }
 EXPORT_SYMBOL_GPL(ide_queue_pc_tail);

 int ide_do_test_unit_ready(ide_drive_t *drive, struct gendisk *disk)
 {
 	struct ide_atapi_pc pc;

 	ide_init_pc(&pc);
 	pc.c[0] = TEST_UNIT_READY;

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

 int ide_do_start_stop(ide_drive_t *drive, struct gendisk *disk, int start)
 {
 	struct ide_atapi_pc pc;

 	ide_init_pc(&pc);
 	pc.c[0] = START_STOP;
 	pc.c[4] = start;

 	if (drive->media == ide_tape)
 		pc.flags |= PC_FLAG_WAIT_FOR_DSC;

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

 int ide_set_media_lock(ide_drive_t *drive, struct gendisk *disk, int on)
 {
 	struct ide_atapi_pc pc;

 	if ((drive->dev_flags & IDE_DFLAG_DOORLOCKING) == 0)
 		return 0;

 	ide_init_pc(&pc);
 	pc.c[0] = ALLOW_MEDIUM_REMOVAL;
 	pc.c[4] = on;

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

 void ide_create_request_sense_cmd(ide_drive_t *drive, struct ide_atapi_pc *pc)
 {
 	ide_init_pc(pc);
 	pc->c[0] = REQUEST_SENSE;
 	if (drive->media == ide_floppy) {
 		pc->c[4] = 255;
 		pc->req_xfer = 18;
 	} else {
 		pc->c[4] = 20;
 		pc->req_xfer = 20;
 	}
 }
 EXPORT_SYMBOL_GPL(ide_create_request_sense_cmd);

 void ide_prep_sense(ide_drive_t *drive, struct request *rq)
 {
 	struct request_sense *sense = &drive->sense_data;
 	struct request *sense_rq = drive->sense_rq;
 	struct scsi_request *req = scsi_req(sense_rq);
 	unsigned int cmd_len, sense_len;
 	int err;

 	switch (drive->media) {
 	case ide_floppy:
 		cmd_len = 255;
 		sense_len = 18;
 		break;
 	case ide_tape:
 		cmd_len = 20;
 		sense_len = 20;
 		break;
 	default:
 		cmd_len = 18;
 		sense_len = 18;
 	}

 	BUG_ON(sense_len > sizeof(*sense));

 	if (rq->cmd_type == REQ_TYPE_ATA_SENSE || drive->sense_rq_armed)
 		return;

 	memset(sense, 0, sizeof(*sense));

 	blk_rq_init(rq->q, sense_rq);
 	scsi_req_init(sense_rq);

 	err = blk_rq_map_kern(drive->queue, sense_rq, sense, sense_len,
 			      GFP_NOIO);
 	if (unlikely(err)) {
 		if (printk_ratelimit())
 			printk(KERN_WARNING PFX "%s: failed to map sense "
 					    "buffer\n", drive->name);
 		return;
 	}

 	sense_rq->rq_disk = rq->rq_disk;
 	sense_rq->cmd_type = REQ_TYPE_ATA_SENSE;
 	sense_rq->rq_flags |= RQF_PREEMPT;

 	req->cmd[0] = GPCMD_REQUEST_SENSE;
 	req->cmd[4] = cmd_len;
 	if (drive->media == ide_tape)
 		req->cmd[13] = REQ_IDETAPE_PC1;

 	drive->sense_rq_armed = true;
 }
 EXPORT_SYMBOL_GPL(ide_prep_sense);

 int ide_queue_sense_rq(ide_drive_t *drive, void *special)
 {
 	/* deferred failure from ide_prep_sense() */
 	if (!drive->sense_rq_armed) {
 		printk(KERN_WARNING PFX "%s: error queuing a sense request\n",
 		       drive->name);
 		return -ENOMEM;
 	}

 	drive->sense_rq->special = special;
 	drive->sense_rq_armed = false;

 	drive->hwif->rq = NULL;

 	elv_add_request(drive->queue, drive->sense_rq, ELEVATOR_INSERT_FRONT);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ide_queue_sense_rq);

 /*
  * Called when an error was detected during the last packet command.
  * We queue a request sense packet command at the head of the request
  * queue.
  */
 void ide_retry_pc(ide_drive_t *drive)
 {
 	struct request *failed_rq = drive->hwif->rq;
 	struct request *sense_rq = drive->sense_rq;
 	struct ide_atapi_pc *pc = &drive->request_sense_pc;

 	(void)ide_read_error(drive);

 	/* init pc from sense_rq */
 	ide_init_pc(pc);
 	memcpy(pc->c, scsi_req(sense_rq)->cmd, 12);

 	if (drive->media == ide_tape)
 		drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;

 	/*
 	 * Push back the failed request and put request sense on top
 	 * of it.  The failed command will be retried after sense data
 	 * is acquired.
 	 */
 	drive->hwif->rq = NULL;
 	ide_requeue_and_plug(drive, failed_rq);
 	if (ide_queue_sense_rq(drive, pc)) {
 		blk_start_request(failed_rq);
 		ide_complete_rq(drive, -EIO, blk_rq_bytes(failed_rq));
 	}
 }
 EXPORT_SYMBOL_GPL(ide_retry_pc);

 int ide_cd_expiry(ide_drive_t *drive)
 {
 	struct request *rq = drive->hwif->rq;
 	unsigned long wait = 0;

 	debug_log("%s: rq->cmd[0]: 0x%x\n", __func__, rq->cmd[0]);

 	/*
 	 * Some commands are *slow* and normally take a long time to complete.
 	 * Usually we can use the ATAPI "disconnect" to bypass this, but not all
 	 * commands/drives support that. Let ide_timer_expiry keep polling us
 	 * for these.
 	 */
 	switch (scsi_req(rq)->cmd[0]) {
 	case GPCMD_BLANK:
 	case GPCMD_FORMAT_UNIT:
 	case GPCMD_RESERVE_RZONE_TRACK:
 	case GPCMD_CLOSE_TRACK:
 	case GPCMD_FLUSH_CACHE:
 		wait = ATAPI_WAIT_PC;
 		break;
 	default:
 		if (!(rq->rq_flags & RQF_QUIET))
 			printk(KERN_INFO PFX "cmd 0x%x timed out\n",
 					 scsi_req(rq)->cmd[0]);
 		wait = 0;
 		break;
 	}
 	return wait;
 }
 EXPORT_SYMBOL_GPL(ide_cd_expiry);

 int ide_cd_get_xferlen(struct request *rq)
 {
 	switch (rq->cmd_type) {
 	case REQ_TYPE_FS:
 		return 32768;
 	case REQ_TYPE_ATA_SENSE:
 	case REQ_TYPE_BLOCK_PC:
 	case REQ_TYPE_ATA_PC:
 		return blk_rq_bytes(rq);
 	default:
 		return 0;
 	}
 }
 EXPORT_SYMBOL_GPL(ide_cd_get_xferlen);

 void ide_read_bcount_and_ireason(ide_drive_t *drive, u16 *bcount, u8 *ireason)
 {
 	struct ide_taskfile tf;

 	drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT |
 				     IDE_VALID_LBAM | IDE_VALID_LBAH);

 	*bcount = (tf.lbah << 8) | tf.lbam;
 	*ireason = tf.nsect & 3;
 }
 EXPORT_SYMBOL_GPL(ide_read_bcount_and_ireason);

 /*
  * Check the contents of the interrupt reason register and attempt to recover if
  * there are problems.
  *
  * Returns:
  * - 0 if everything's ok
  * - 1 if the request has to be terminated.
  */
 int ide_check_ireason(ide_drive_t *drive, struct request *rq, int len,
 		      int ireason, int rw)
 {
 	ide_hwif_t *hwif = drive->hwif;

 	debug_log("ireason: 0x%x, rw: 0x%x\n", ireason, rw);

 	if (ireason == (!rw << 1))
 		return 0;
 	else if (ireason == (rw << 1)) {
 		printk(KERN_ERR PFX "%s: %s: wrong transfer direction!\n",
 				drive->name, __func__);

 		if (dev_is_idecd(drive))
 			ide_pad_transfer(drive, rw, len);
 	} else if (!rw && ireason == ATAPI_COD) {
 		if (dev_is_idecd(drive)) {
 			/*
 			 * Some drives (ASUS) seem to tell us that status info
 			 * is available.  Just get it and ignore.
 			 */
 			(void)hwif->tp_ops->read_status(hwif);
 			return 0;
 		}
 	} else {
 		if (ireason & ATAPI_COD)
 			printk(KERN_ERR PFX "%s: CoD != 0 in %s\n", drive->name,
 					__func__);

 		/* drive wants a command packet, or invalid ireason... */
 		printk(KERN_ERR PFX "%s: %s: bad interrupt reason 0x%02x\n",
 				drive->name, __func__, ireason);
 	}

 	if (dev_is_idecd(drive) && rq->cmd_type == REQ_TYPE_ATA_PC)
 		rq->rq_flags |= RQF_FAILED;

 	return 1;
 }
 EXPORT_SYMBOL_GPL(ide_check_ireason);

 /*
  * 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.
  */
 static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
 {
 	struct ide_atapi_pc *pc = drive->pc;
 	ide_hwif_t *hwif = drive->hwif;
 	struct ide_cmd *cmd = &hwif->cmd;
 	struct request *rq = hwif->rq;
 	const struct ide_tp_ops *tp_ops = hwif->tp_ops;
 	unsigned int timeout, done;
 	u16 bcount;
 	u8 stat, ireason, dsc = 0;
 	u8 write = !!(pc->flags & PC_FLAG_WRITING);

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

 	timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
 					       : WAIT_TAPE_CMD;

 	/* Clear the interrupt */
 	stat = tp_ops->read_status(hwif);

 	if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
 		int rc;

 		drive->waiting_for_dma = 0;
 		rc = hwif->dma_ops->dma_end(drive);
 		ide_dma_unmap_sg(drive, cmd);

 		if (rc || (drive->media == ide_tape && (stat & ATA_ERR))) {
 			if (drive->media == ide_floppy)
 				printk(KERN_ERR PFX "%s: DMA %s error\n",
 					drive->name, rq_data_dir(pc->rq)
 						     ? "write" : "read");
 			pc->flags |= PC_FLAG_DMA_ERROR;
 		} else
 			scsi_req(rq)->resid_len = 0;
 		debug_log("%s: DMA finished\n", drive->name);
 	}

 	/* No more interrupts */
 	if ((stat & ATA_DRQ) == 0) {
 		int uptodate, error;

 		debug_log("Packet command completed, %d bytes transferred\n",
 			  blk_rq_bytes(rq));

 		pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;

 		local_irq_enable_in_hardirq();

 		if (drive->media == ide_tape &&
 		    (stat & ATA_ERR) && scsi_req(rq)->cmd[0] == REQUEST_SENSE)
 			stat &= ~ATA_ERR;

 		if ((stat & ATA_ERR) || (pc->flags & PC_FLAG_DMA_ERROR)) {
 			/* Error detected */
 			debug_log("%s: I/O error\n", drive->name);

 			if (drive->media != ide_tape)
 				pc->rq->errors++;

 			if (scsi_req(rq)->cmd[0] == REQUEST_SENSE) {
 				printk(KERN_ERR PFX "%s: I/O error in request "
 						"sense command\n", drive->name);
 				return ide_do_reset(drive);
 			}

 			debug_log("[cmd %x]: check condition\n", rq->cmd[0]);

 			/* Retry operation */
 			ide_retry_pc(drive);

 			/* queued, but not started */
 			return ide_stopped;
 		}
 		pc->error = 0;

 		if ((pc->flags & PC_FLAG_WAIT_FOR_DSC) && (stat & ATA_DSC) == 0)
 			dsc = 1;

 		/*
 		 * ->pc_callback() might change rq->data_len for
 		 * residual count, cache total length.
 		 */
 		done = blk_rq_bytes(rq);

 		/* Command finished - Call the callback function */
 		uptodate = drive->pc_callback(drive, dsc);

 		if (uptodate == 0)
 			drive->failed_pc = NULL;

 		if (rq->cmd_type == REQ_TYPE_DRV_PRIV) {
 			rq->errors = 0;
 			error = 0;
 		} else {

 			if (rq->cmd_type != REQ_TYPE_FS && uptodate <= 0) {
 				if (rq->errors == 0)
 					rq->errors = -EIO;
 			}

 			error = uptodate ? 0 : -EIO;
 		}

 		ide_complete_rq(drive, error, blk_rq_bytes(rq));
 		return ide_stopped;
 	}

 	if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
 		pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;
 		printk(KERN_ERR PFX "%s: The device wants to issue more "
 				"interrupts in DMA mode\n", drive->name);
 		ide_dma_off(drive);
 		return ide_do_reset(drive);
 	}

 	/* Get the number of bytes to transfer on this interrupt. */
 	ide_read_bcount_and_ireason(drive, &bcount, &ireason);

 	if (ide_check_ireason(drive, rq, bcount, ireason, write))
 		return ide_do_reset(drive);

 	done = min_t(unsigned int, bcount, cmd->nleft);
 	ide_pio_bytes(drive, cmd, write, done);

 	/* Update transferred byte count */
 	scsi_req(rq)->resid_len -= done;

 	bcount -= done;

 	if (bcount)
 		ide_pad_transfer(drive, write, bcount);

 	debug_log("[cmd %x] transferred %d bytes, padded %d bytes, resid: %u\n",
 		  rq->cmd[0], done, bcount, scsi_req(rq)->resid_len);

 	/* And set the interrupt handler again */
 	ide_set_handler(drive, ide_pc_intr, timeout);
 	return ide_started;
 }

 static void ide_init_packet_cmd(struct ide_cmd *cmd, u8 valid_tf,
 				u16 bcount, u8 dma)
 {
 	cmd->protocol = dma ? ATAPI_PROT_DMA : ATAPI_PROT_PIO;
 	cmd->valid.out.tf = IDE_VALID_LBAH | IDE_VALID_LBAM |
 			    IDE_VALID_FEATURE | valid_tf;
 	cmd->tf.command = ATA_CMD_PACKET;
 	cmd->tf.feature = dma;		/* Use PIO/DMA */
 	cmd->tf.lbam    = bcount & 0xff;
 	cmd->tf.lbah    = (bcount >> 8) & 0xff;
 }

 static u8 ide_read_ireason(ide_drive_t *drive)
 {
 	struct ide_taskfile tf;

 	drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT);

 	return tf.nsect & 3;
 }

 static u8 ide_wait_ireason(ide_drive_t *drive, u8 ireason)
 {
 	int retries = 100;

 	while (retries-- && ((ireason & ATAPI_COD) == 0 ||
 		(ireason & ATAPI_IO))) {
 		printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing "
 				"a packet command, retrying\n", drive->name);
 		udelay(100);
 		ireason = ide_read_ireason(drive);
 		if (retries == 0) {
 			printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing"
 					" a packet command, ignoring\n",
 					drive->name);
 			ireason |= ATAPI_COD;
 			ireason &= ~ATAPI_IO;
 		}
 	}

 	return ireason;
 }

 static int ide_delayed_transfer_pc(ide_drive_t *drive)
 {
 	/* Send the actual packet */
 	drive->hwif->tp_ops->output_data(drive, NULL, drive->pc->c, 12);

 	/* Timeout for the packet command */
 	return WAIT_FLOPPY_CMD;
 }

 static ide_startstop_t ide_transfer_pc(ide_drive_t *drive)
 {
 	struct ide_atapi_pc *uninitialized_var(pc);
 	ide_hwif_t *hwif = drive->hwif;
 	struct request *rq = hwif->rq;
 	ide_expiry_t *expiry;
 	unsigned int timeout;
 	int cmd_len;
 	ide_startstop_t startstop;
 	u8 ireason;

 	if (ide_wait_stat(&startstop, drive, ATA_DRQ, ATA_BUSY, WAIT_READY)) {
 		printk(KERN_ERR PFX "%s: Strange, packet command initiated yet "
 				"DRQ isn't asserted\n", drive->name);
 		return startstop;
 	}

 	if (drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT) {
 		if (drive->dma)
 			drive->waiting_for_dma = 1;
 	}

 	if (dev_is_idecd(drive)) {
 		/* ATAPI commands get padded out to 12 bytes minimum */
 		cmd_len = COMMAND_SIZE(scsi_req(rq)->cmd[0]);
 		if (cmd_len < ATAPI_MIN_CDB_BYTES)
 			cmd_len = ATAPI_MIN_CDB_BYTES;

 		timeout = rq->timeout;
 		expiry  = ide_cd_expiry;
 	} else {
 		pc = drive->pc;

 		cmd_len = ATAPI_MIN_CDB_BYTES;

 		/*
 		 * If necessary schedule the packet transfer to occur 'timeout'
 		 * milliseconds later in ide_delayed_transfer_pc() after the
 		 * device says it's ready for a packet.
 		 */
 		if (drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) {
 			timeout = drive->pc_delay;
 			expiry = &ide_delayed_transfer_pc;
 		} else {
 			timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
 							       : WAIT_TAPE_CMD;
 			expiry = NULL;
 		}

 		ireason = ide_read_ireason(drive);
 		if (drive->media == ide_tape)
 			ireason = ide_wait_ireason(drive, ireason);

 		if ((ireason & ATAPI_COD) == 0 || (ireason & ATAPI_IO)) {
 			printk(KERN_ERR PFX "%s: (IO,CoD) != (0,1) while "
 				"issuing a packet command\n", drive->name);

 			return ide_do_reset(drive);
 		}
 	}

 	hwif->expiry = expiry;

 	/* Set the interrupt routine */
 	ide_set_handler(drive,
 			(dev_is_idecd(drive) ? drive->irq_handler
 					     : ide_pc_intr),
 			timeout);

 	/* Send the actual packet */
 	if ((drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) == 0)
 		hwif->tp_ops->output_data(drive, NULL, scsi_req(rq)->cmd, cmd_len);

 	/* Begin DMA, if necessary */
 	if (dev_is_idecd(drive)) {
 		if (drive->dma)
 			hwif->dma_ops->dma_start(drive);
 	} else {
 		if (pc->flags & PC_FLAG_DMA_OK) {
 			pc->flags |= PC_FLAG_DMA_IN_PROGRESS;
 			hwif->dma_ops->dma_start(drive);
 		}
 	}

 	return ide_started;
 }

 ide_startstop_t ide_issue_pc(ide_drive_t *drive, struct ide_cmd *cmd)
 {
 	struct ide_atapi_pc *pc;
 	ide_hwif_t *hwif = drive->hwif;
 	ide_expiry_t *expiry = NULL;
 	struct request *rq = hwif->rq;
 	unsigned int timeout, bytes;
 	u16 bcount;
 	u8 valid_tf;
 	u8 drq_int = !!(drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT);

 	if (dev_is_idecd(drive)) {
 		valid_tf = IDE_VALID_NSECT | IDE_VALID_LBAL;
 		bcount = ide_cd_get_xferlen(rq);
 		expiry = ide_cd_expiry;
 		timeout = ATAPI_WAIT_PC;

 		if (drive->dma)
 			drive->dma = !ide_dma_prepare(drive, cmd);
 	} else {
 		pc = drive->pc;

 		valid_tf = IDE_VALID_DEVICE;
 		bytes = blk_rq_bytes(rq);
 		bcount = ((drive->media == ide_tape) ? bytes
 						     : min_t(unsigned int,
 							     bytes, 63 * 1024));

 		/* We haven't transferred any data yet */
 		scsi_req(rq)->resid_len = bcount;

 		if (pc->flags & PC_FLAG_DMA_ERROR) {
 			pc->flags &= ~PC_FLAG_DMA_ERROR;
 			ide_dma_off(drive);
 		}

 		if (pc->flags & PC_FLAG_DMA_OK)
 			drive->dma = !ide_dma_prepare(drive, cmd);

 		if (!drive->dma)
 			pc->flags &= ~PC_FLAG_DMA_OK;

 		timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
 						       : WAIT_TAPE_CMD;
 	}

 	ide_init_packet_cmd(cmd, valid_tf, bcount, drive->dma);

 	(void)do_rw_taskfile(drive, cmd);

 	if (drq_int) {
 		if (drive->dma)
 			drive->waiting_for_dma = 0;
 		hwif->expiry = expiry;
 	}

 	ide_execute_command(drive, cmd, ide_transfer_pc, timeout);

 	return drq_int ? ide_started : ide_transfer_pc(drive);
 }
 EXPORT_SYMBOL_GPL(ide_issue_pc);
	/*
	* ATAPI support.
	*/

	#include <linux/kernel.h>
	#include <linux/cdrom.h>
	#include <linux/delay.h>
	#include <linux/export.h>
	#include <linux/ide.h>
	#include <linux/scatterlist.h>
	#include <linux/gfp.h>

	#include <scsi/scsi.h>

	#define DRV_NAME "ide-atapi"
	#define PFX DRV_NAME ": "

	#ifdef DEBUG
	#define debug_log(fmt, args...) \
	printk(KERN_INFO "ide: " fmt, ## args)
	#else
	#define debug_log(fmt, args...) do {} while (0)
	#endif

	#define ATAPI_MIN_CDB_BYTES 12

	static inline int dev_is_idecd(ide_drive_t *drive)
	{
	return drive->media == ide_cdrom \|\| drive->media == ide_optical;
	}

	/*
	* Check whether we can support a device,
	* based on the ATAPI IDENTIFY command results.
	*/
	int ide_check_atapi_device(ide_drive_t drive, const char s)
	{
	u16 *id = drive->id;
	u8 gcw[2], protocol, device_type, removable, drq_type, packet_size;

	((u16 )&gcw) = id[ATA_ID_CONFIG];

	protocol = (gcw[1] & 0xC0) >> 6;
	device_type = gcw[1] & 0x1F;
	removable = (gcw[0] & 0x80) >> 7;
	drq_type = (gcw[0] & 0x60) >> 5;
	packet_size = gcw[0] & 0x03;

	#ifdef CONFIG_PPC
	/* kludge for Apple PowerBook internal zip */
	if (drive->media == ide_floppy && device_type == 5 &&
	!strstr((char *)&id[ATA_ID_PROD], "CD-ROM") &&
	strstr((char *)&id[ATA_ID_PROD], "ZIP"))
	device_type = 0;
	#endif

	if (protocol != 2)
	printk(KERN_ERR "%s: %s: protocol (0x%02x) is not ATAPI\n",
	s, drive->name, protocol);
	else if ((drive->media == ide_floppy && device_type != 0) \|\|
	(drive->media == ide_tape && device_type != 1))
	printk(KERN_ERR "%s: %s: invalid device type (0x%02x)\n",
	s, drive->name, device_type);
	else if (removable == 0)
	printk(KERN_ERR "%s: %s: the removable flag is not set\n",
	s, drive->name);
	else if (drive->media == ide_floppy && drq_type == 3)
	printk(KERN_ERR "%s: %s: sorry, DRQ type (0x%02x) not "
	"supported\n", s, drive->name, drq_type);
	else if (packet_size != 0)
	printk(KERN_ERR "%s: %s: packet size (0x%02x) is not 12 "
	"bytes\n", s, drive->name, packet_size);
	else
	return 1;
	return 0;
	}
	EXPORT_SYMBOL_GPL(ide_check_atapi_device);

	void ide_init_pc(struct ide_atapi_pc *pc)
	{
	memset(pc, 0, sizeof(*pc));
	}
	EXPORT_SYMBOL_GPL(ide_init_pc);

	/*
	* Add a special packet command request to the tail of the request queue,
	* and wait for it to be serviced.
	*/
	int ide_queue_pc_tail(ide_drive_t drive, struct gendisk disk,
	struct ide_atapi_pc pc, void buf, unsigned int bufflen)
	{
	struct request *rq;
	int error;

	rq = blk_get_request(drive->queue, READ, __GFP_RECLAIM);
	scsi_req_init(rq);
	rq->cmd_type = REQ_TYPE_DRV_PRIV;
	rq->special = (char *)pc;

	if (buf && bufflen) {
	error = blk_rq_map_kern(drive->queue, rq, buf, bufflen,
	GFP_NOIO);
	if (error)
	goto put_req;
	}

	memcpy(scsi_req(rq)->cmd, pc->c, 12);
	if (drive->media == ide_tape)
	scsi_req(rq)->cmd[13] = REQ_IDETAPE_PC1;
	error = blk_execute_rq(drive->queue, disk, rq, 0);
	put_req:
	blk_put_request(rq);
	return error;
	}
	EXPORT_SYMBOL_GPL(ide_queue_pc_tail);

	int ide_do_test_unit_ready(ide_drive_t drive, struct gendisk disk)
	{
	struct ide_atapi_pc pc;

	ide_init_pc(&pc);
	pc.c[0] = TEST_UNIT_READY;

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

	int ide_do_start_stop(ide_drive_t drive, struct gendisk disk, int start)
	{
	struct ide_atapi_pc pc;

	ide_init_pc(&pc);
	pc.c[0] = START_STOP;
	pc.c[4] = start;

	if (drive->media == ide_tape)
	pc.flags \|= PC_FLAG_WAIT_FOR_DSC;

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

	int ide_set_media_lock(ide_drive_t drive, struct gendisk disk, int on)
	{
	struct ide_atapi_pc pc;

	if ((drive->dev_flags & IDE_DFLAG_DOORLOCKING) == 0)
	return 0;

	ide_init_pc(&pc);
	pc.c[0] = ALLOW_MEDIUM_REMOVAL;
	pc.c[4] = on;

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

	void ide_create_request_sense_cmd(ide_drive_t drive, struct ide_atapi_pc pc)
	{
	ide_init_pc(pc);
	pc->c[0] = REQUEST_SENSE;
	if (drive->media == ide_floppy) {
	pc->c[4] = 255;
	pc->req_xfer = 18;
	} else {
	pc->c[4] = 20;
	pc->req_xfer = 20;
	}
	}
	EXPORT_SYMBOL_GPL(ide_create_request_sense_cmd);

	void ide_prep_sense(ide_drive_t drive, struct request rq)
	{
	struct request_sense *sense = &drive->sense_data;
	struct request *sense_rq = drive->sense_rq;
	struct scsi_request *req = scsi_req(sense_rq);
	unsigned int cmd_len, sense_len;
	int err;

	switch (drive->media) {
	case ide_floppy:
	cmd_len = 255;
	sense_len = 18;
	break;
	case ide_tape:
	cmd_len = 20;
	sense_len = 20;
	break;
	default:
	cmd_len = 18;
	sense_len = 18;
	}

	BUG_ON(sense_len > sizeof(*sense));

	if (rq->cmd_type == REQ_TYPE_ATA_SENSE \|\| drive->sense_rq_armed)
	return;

	memset(sense, 0, sizeof(*sense));

	blk_rq_init(rq->q, sense_rq);
	scsi_req_init(sense_rq);

	err = blk_rq_map_kern(drive->queue, sense_rq, sense, sense_len,
	GFP_NOIO);
	if (unlikely(err)) {
	if (printk_ratelimit())
	printk(KERN_WARNING PFX "%s: failed to map sense "
	"buffer\n", drive->name);
	return;
	}

	sense_rq->rq_disk = rq->rq_disk;
	sense_rq->cmd_type = REQ_TYPE_ATA_SENSE;
	sense_rq->rq_flags \|= RQF_PREEMPT;

	req->cmd[0] = GPCMD_REQUEST_SENSE;
	req->cmd[4] = cmd_len;
	if (drive->media == ide_tape)
	req->cmd[13] = REQ_IDETAPE_PC1;

	drive->sense_rq_armed = true;
	}
	EXPORT_SYMBOL_GPL(ide_prep_sense);

	int ide_queue_sense_rq(ide_drive_t drive, void special)
	{
	/* deferred failure from ide_prep_sense() */
	if (!drive->sense_rq_armed) {
	printk(KERN_WARNING PFX "%s: error queuing a sense request\n",
	drive->name);
	return -ENOMEM;
	}

	drive->sense_rq->special = special;
	drive->sense_rq_armed = false;

	drive->hwif->rq = NULL;

	elv_add_request(drive->queue, drive->sense_rq, ELEVATOR_INSERT_FRONT);
	return 0;
	}
	EXPORT_SYMBOL_GPL(ide_queue_sense_rq);

	/*
	* Called when an error was detected during the last packet command.
	* We queue a request sense packet command at the head of the request
	* queue.
	*/
	void ide_retry_pc(ide_drive_t *drive)
	{
	struct request *failed_rq = drive->hwif->rq;
	struct request *sense_rq = drive->sense_rq;
	struct ide_atapi_pc *pc = &drive->request_sense_pc;

	(void)ide_read_error(drive);

	/* init pc from sense_rq */
	ide_init_pc(pc);
	memcpy(pc->c, scsi_req(sense_rq)->cmd, 12);

	if (drive->media == ide_tape)
	drive->atapi_flags \|= IDE_AFLAG_IGNORE_DSC;

	/*
	* Push back the failed request and put request sense on top
	* of it. The failed command will be retried after sense data
	* is acquired.
	*/
	drive->hwif->rq = NULL;
	ide_requeue_and_plug(drive, failed_rq);
	if (ide_queue_sense_rq(drive, pc)) {
	blk_start_request(failed_rq);
	ide_complete_rq(drive, -EIO, blk_rq_bytes(failed_rq));
	}
	}
	EXPORT_SYMBOL_GPL(ide_retry_pc);

	int ide_cd_expiry(ide_drive_t *drive)
	{
	struct request *rq = drive->hwif->rq;
	unsigned long wait = 0;

	debug_log("%s: rq->cmd[0]: 0x%x\n", __func__, rq->cmd[0]);

	/*
	* Some commands are slow and normally take a long time to complete.
	* Usually we can use the ATAPI "disconnect" to bypass this, but not all
	* commands/drives support that. Let ide_timer_expiry keep polling us
	* for these.
	*/
	switch (scsi_req(rq)->cmd[0]) {
	case GPCMD_BLANK:
	case GPCMD_FORMAT_UNIT:
	case GPCMD_RESERVE_RZONE_TRACK:
	case GPCMD_CLOSE_TRACK:
	case GPCMD_FLUSH_CACHE:
	wait = ATAPI_WAIT_PC;
	break;
	default:
	if (!(rq->rq_flags & RQF_QUIET))
	printk(KERN_INFO PFX "cmd 0x%x timed out\n",
	scsi_req(rq)->cmd[0]);
	wait = 0;
	break;
	}
	return wait;
	}
	EXPORT_SYMBOL_GPL(ide_cd_expiry);

	int ide_cd_get_xferlen(struct request *rq)
	{
	switch (rq->cmd_type) {
	case REQ_TYPE_FS:
	return 32768;
	case REQ_TYPE_ATA_SENSE:
	case REQ_TYPE_BLOCK_PC:
	case REQ_TYPE_ATA_PC:
	return blk_rq_bytes(rq);
	default:
	return 0;
	}
	}
	EXPORT_SYMBOL_GPL(ide_cd_get_xferlen);

	void ide_read_bcount_and_ireason(ide_drive_t drive, u16 bcount, u8 *ireason)
	{
	struct ide_taskfile tf;

	drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT \|
	IDE_VALID_LBAM \| IDE_VALID_LBAH);

	*bcount = (tf.lbah << 8) \| tf.lbam;
	*ireason = tf.nsect & 3;
	}
	EXPORT_SYMBOL_GPL(ide_read_bcount_and_ireason);

	/*
	* Check the contents of the interrupt reason register and attempt to recover if
	* there are problems.
	*
	* Returns:
	* - 0 if everything's ok
	* - 1 if the request has to be terminated.
	*/
	int ide_check_ireason(ide_drive_t drive, struct request rq, int len,
	int ireason, int rw)
	{
	ide_hwif_t *hwif = drive->hwif;

	debug_log("ireason: 0x%x, rw: 0x%x\n", ireason, rw);

	if (ireason == (!rw << 1))
	return 0;
	else if (ireason == (rw << 1)) {
	printk(KERN_ERR PFX "%s: %s: wrong transfer direction!\n",
	drive->name, __func__);

	if (dev_is_idecd(drive))
	ide_pad_transfer(drive, rw, len);
	} else if (!rw && ireason == ATAPI_COD) {
	if (dev_is_idecd(drive)) {
	/*
	* Some drives (ASUS) seem to tell us that status info
	* is available. Just get it and ignore.
	*/
	(void)hwif->tp_ops->read_status(hwif);
	return 0;
	}
	} else {
	if (ireason & ATAPI_COD)
	printk(KERN_ERR PFX "%s: CoD != 0 in %s\n", drive->name,
	__func__);

	/* drive wants a command packet, or invalid ireason... */
	printk(KERN_ERR PFX "%s: %s: bad interrupt reason 0x%02x\n",
	drive->name, __func__, ireason);
	}

	if (dev_is_idecd(drive) && rq->cmd_type == REQ_TYPE_ATA_PC)
	rq->rq_flags \|= RQF_FAILED;

	return 1;
	}
	EXPORT_SYMBOL_GPL(ide_check_ireason);

	/*
	* 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.
	*/
	static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
	{
	struct ide_atapi_pc *pc = drive->pc;
	ide_hwif_t *hwif = drive->hwif;
	struct ide_cmd *cmd = &hwif->cmd;
	struct request *rq = hwif->rq;
	const struct ide_tp_ops *tp_ops = hwif->tp_ops;
	unsigned int timeout, done;
	u16 bcount;
	u8 stat, ireason, dsc = 0;
	u8 write = !!(pc->flags & PC_FLAG_WRITING);

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

	timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
	: WAIT_TAPE_CMD;

	/* Clear the interrupt */
	stat = tp_ops->read_status(hwif);

	if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
	int rc;

	drive->waiting_for_dma = 0;
	rc = hwif->dma_ops->dma_end(drive);
	ide_dma_unmap_sg(drive, cmd);

	if (rc \|\| (drive->media == ide_tape && (stat & ATA_ERR))) {
	if (drive->media == ide_floppy)
	printk(KERN_ERR PFX "%s: DMA %s error\n",
	drive->name, rq_data_dir(pc->rq)
	? "write" : "read");
	pc->flags \|= PC_FLAG_DMA_ERROR;
	} else
	scsi_req(rq)->resid_len = 0;
	debug_log("%s: DMA finished\n", drive->name);
	}

	/* No more interrupts */
	if ((stat & ATA_DRQ) == 0) {
	int uptodate, error;

	debug_log("Packet command completed, %d bytes transferred\n",
	blk_rq_bytes(rq));

	pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;

	local_irq_enable_in_hardirq();

	if (drive->media == ide_tape &&
	(stat & ATA_ERR) && scsi_req(rq)->cmd[0] == REQUEST_SENSE)
	stat &= ~ATA_ERR;

	if ((stat & ATA_ERR) \|\| (pc->flags & PC_FLAG_DMA_ERROR)) {
	/* Error detected */
	debug_log("%s: I/O error\n", drive->name);

	if (drive->media != ide_tape)
	pc->rq->errors++;

	if (scsi_req(rq)->cmd[0] == REQUEST_SENSE) {
	printk(KERN_ERR PFX "%s: I/O error in request "
	"sense command\n", drive->name);
	return ide_do_reset(drive);
	}

	debug_log("[cmd %x]: check condition\n", rq->cmd[0]);

	/* Retry operation */
	ide_retry_pc(drive);

	/* queued, but not started */
	return ide_stopped;
	}
	pc->error = 0;

	if ((pc->flags & PC_FLAG_WAIT_FOR_DSC) && (stat & ATA_DSC) == 0)
	dsc = 1;

	/*
	* ->pc_callback() might change rq->data_len for
	* residual count, cache total length.
	*/
	done = blk_rq_bytes(rq);

	/* Command finished - Call the callback function */
	uptodate = drive->pc_callback(drive, dsc);

	if (uptodate == 0)
	drive->failed_pc = NULL;

	if (rq->cmd_type == REQ_TYPE_DRV_PRIV) {
	rq->errors = 0;
	error = 0;
	} else {

	if (rq->cmd_type != REQ_TYPE_FS && uptodate <= 0) {
	if (rq->errors == 0)
	rq->errors = -EIO;
	}

	error = uptodate ? 0 : -EIO;
	}

	ide_complete_rq(drive, error, blk_rq_bytes(rq));
	return ide_stopped;
	}

	if (pc->flags & PC_FLAG_DMA_IN_PROGRESS) {
	pc->flags &= ~PC_FLAG_DMA_IN_PROGRESS;
	printk(KERN_ERR PFX "%s: The device wants to issue more "
	"interrupts in DMA mode\n", drive->name);
	ide_dma_off(drive);
	return ide_do_reset(drive);
	}

	/* Get the number of bytes to transfer on this interrupt. */
	ide_read_bcount_and_ireason(drive, &bcount, &ireason);

	if (ide_check_ireason(drive, rq, bcount, ireason, write))
	return ide_do_reset(drive);

	done = min_t(unsigned int, bcount, cmd->nleft);
	ide_pio_bytes(drive, cmd, write, done);

	/* Update transferred byte count */
	scsi_req(rq)->resid_len -= done;

	bcount -= done;

	if (bcount)
	ide_pad_transfer(drive, write, bcount);

	debug_log("[cmd %x] transferred %d bytes, padded %d bytes, resid: %u\n",
	rq->cmd[0], done, bcount, scsi_req(rq)->resid_len);

	/* And set the interrupt handler again */
	ide_set_handler(drive, ide_pc_intr, timeout);
	return ide_started;
	}

	static void ide_init_packet_cmd(struct ide_cmd *cmd, u8 valid_tf,
	u16 bcount, u8 dma)
	{
	cmd->protocol = dma ? ATAPI_PROT_DMA : ATAPI_PROT_PIO;
	cmd->valid.out.tf = IDE_VALID_LBAH \| IDE_VALID_LBAM \|
	IDE_VALID_FEATURE \| valid_tf;
	cmd->tf.command = ATA_CMD_PACKET;
	cmd->tf.feature = dma; /* Use PIO/DMA */
	cmd->tf.lbam = bcount & 0xff;
	cmd->tf.lbah = (bcount >> 8) & 0xff;
	}

	static u8 ide_read_ireason(ide_drive_t *drive)
	{
	struct ide_taskfile tf;

	drive->hwif->tp_ops->tf_read(drive, &tf, IDE_VALID_NSECT);

	return tf.nsect & 3;
	}

	static u8 ide_wait_ireason(ide_drive_t *drive, u8 ireason)
	{
	int retries = 100;

	while (retries-- && ((ireason & ATAPI_COD) == 0 \|\|
	(ireason & ATAPI_IO))) {
	printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing "
	"a packet command, retrying\n", drive->name);
	udelay(100);
	ireason = ide_read_ireason(drive);
	if (retries == 0) {
	printk(KERN_ERR PFX "%s: (IO,CoD != (0,1) while issuing"
	" a packet command, ignoring\n",
	drive->name);
	ireason \|= ATAPI_COD;
	ireason &= ~ATAPI_IO;
	}
	}

	return ireason;
	}

	static int ide_delayed_transfer_pc(ide_drive_t *drive)
	{
	/* Send the actual packet */
	drive->hwif->tp_ops->output_data(drive, NULL, drive->pc->c, 12);

	/* Timeout for the packet command */
	return WAIT_FLOPPY_CMD;
	}

	static ide_startstop_t ide_transfer_pc(ide_drive_t *drive)
	{
	struct ide_atapi_pc *uninitialized_var(pc);
	ide_hwif_t *hwif = drive->hwif;
	struct request *rq = hwif->rq;
	ide_expiry_t *expiry;
	unsigned int timeout;
	int cmd_len;
	ide_startstop_t startstop;
	u8 ireason;

	if (ide_wait_stat(&startstop, drive, ATA_DRQ, ATA_BUSY, WAIT_READY)) {
	printk(KERN_ERR PFX "%s: Strange, packet command initiated yet "
	"DRQ isn't asserted\n", drive->name);
	return startstop;
	}

	if (drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT) {
	if (drive->dma)
	drive->waiting_for_dma = 1;
	}

	if (dev_is_idecd(drive)) {
	/* ATAPI commands get padded out to 12 bytes minimum */
	cmd_len = COMMAND_SIZE(scsi_req(rq)->cmd[0]);
	if (cmd_len < ATAPI_MIN_CDB_BYTES)
	cmd_len = ATAPI_MIN_CDB_BYTES;

	timeout = rq->timeout;
	expiry = ide_cd_expiry;
	} else {
	pc = drive->pc;

	cmd_len = ATAPI_MIN_CDB_BYTES;

	/*
	* If necessary schedule the packet transfer to occur 'timeout'
	* milliseconds later in ide_delayed_transfer_pc() after the
	* device says it's ready for a packet.
	*/
	if (drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) {
	timeout = drive->pc_delay;
	expiry = &ide_delayed_transfer_pc;
	} else {
	timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
	: WAIT_TAPE_CMD;
	expiry = NULL;
	}

	ireason = ide_read_ireason(drive);
	if (drive->media == ide_tape)
	ireason = ide_wait_ireason(drive, ireason);

	if ((ireason & ATAPI_COD) == 0 \|\| (ireason & ATAPI_IO)) {
	printk(KERN_ERR PFX "%s: (IO,CoD) != (0,1) while "
	"issuing a packet command\n", drive->name);

	return ide_do_reset(drive);
	}
	}

	hwif->expiry = expiry;

	/* Set the interrupt routine */
	ide_set_handler(drive,
	(dev_is_idecd(drive) ? drive->irq_handler
	: ide_pc_intr),
	timeout);

	/* Send the actual packet */
	if ((drive->atapi_flags & IDE_AFLAG_ZIP_DRIVE) == 0)
	hwif->tp_ops->output_data(drive, NULL, scsi_req(rq)->cmd, cmd_len);

	/* Begin DMA, if necessary */
	if (dev_is_idecd(drive)) {
	if (drive->dma)
	hwif->dma_ops->dma_start(drive);
	} else {
	if (pc->flags & PC_FLAG_DMA_OK) {
	pc->flags \|= PC_FLAG_DMA_IN_PROGRESS;
	hwif->dma_ops->dma_start(drive);
	}
	}

	return ide_started;
	}

	ide_startstop_t ide_issue_pc(ide_drive_t drive, struct ide_cmd cmd)
	{
	struct ide_atapi_pc *pc;
	ide_hwif_t *hwif = drive->hwif;
	ide_expiry_t *expiry = NULL;
	struct request *rq = hwif->rq;
	unsigned int timeout, bytes;
	u16 bcount;
	u8 valid_tf;
	u8 drq_int = !!(drive->atapi_flags & IDE_AFLAG_DRQ_INTERRUPT);

	if (dev_is_idecd(drive)) {
	valid_tf = IDE_VALID_NSECT \| IDE_VALID_LBAL;
	bcount = ide_cd_get_xferlen(rq);
	expiry = ide_cd_expiry;
	timeout = ATAPI_WAIT_PC;

	if (drive->dma)
	drive->dma = !ide_dma_prepare(drive, cmd);
	} else {
	pc = drive->pc;

	valid_tf = IDE_VALID_DEVICE;
	bytes = blk_rq_bytes(rq);
	bcount = ((drive->media == ide_tape) ? bytes
	: min_t(unsigned int,
	bytes, 63 * 1024));

	/* We haven't transferred any data yet */
	scsi_req(rq)->resid_len = bcount;

	if (pc->flags & PC_FLAG_DMA_ERROR) {
	pc->flags &= ~PC_FLAG_DMA_ERROR;
	ide_dma_off(drive);
	}

	if (pc->flags & PC_FLAG_DMA_OK)
	drive->dma = !ide_dma_prepare(drive, cmd);

	if (!drive->dma)
	pc->flags &= ~PC_FLAG_DMA_OK;

	timeout = (drive->media == ide_floppy) ? WAIT_FLOPPY_CMD
	: WAIT_TAPE_CMD;
	}

	ide_init_packet_cmd(cmd, valid_tf, bcount, drive->dma);

	(void)do_rw_taskfile(drive, cmd);

	if (drq_int) {
	if (drive->dma)
	drive->waiting_for_dma = 0;
	hwif->expiry = expiry;
	}

	ide_execute_command(drive, cmd, ide_transfer_pc, timeout);

	return drq_int ? ide_started : ide_transfer_pc(drive);
	}
	EXPORT_SYMBOL_GPL(ide_issue_pc);