/*
   *	IDE I/O functions
   *
   *	Basic PIO and command management functionality.
   *
   * This code was split off from ide.c. See ide.c for history and original
   * copyrights.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the
   * Free Software Foundation; either version 2, or (at your option) any
   * later version.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * For the avoidance of doubt the "preferred form" of this code is one which
   * is in an open non patent encumbered format. Where cryptographic key signing
   * forms part of the process of creating an executable the information
   * including keys needed to generate an equivalently functional executable
   * are deemed to be part of the source code.
   */
   
   

  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/string.h>
  #include <linux/kernel.h>
  #include <linux/timer.h>
  #include <linux/mm.h>
  #include <linux/interrupt.h>
  #include <linux/major.h>
  #include <linux/errno.h>
  #include <linux/genhd.h>
  #include <linux/blkpg.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/pci.h>
  #include <linux/delay.h>
  #include <linux/ide.h>
  #include <linux/completion.h>
  #include <linux/reboot.h>
  #include <linux/cdrom.h>
  #include <linux/seq_file.h>
  #include <linux/device.h>
  #include <linux/kmod.h>
  #include <linux/scatterlist.h>

  #include <linux/bitops.h>

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

  int ide_end_rq(ide_drive_t *drive, struct request *rq, int error,

  	       unsigned int nr_bytes)

  {

  	/*
  	 * decide whether to reenable DMA -- 3 is a random magic for now,
  	 * if we DMA timeout more than 3 times, just stay in PIO
  	 */

  	if ((drive->dev_flags & IDE_DFLAG_DMA_PIO_RETRY) &&
  	    drive->retry_pio <= 3) {
  		drive->dev_flags &= ~IDE_DFLAG_DMA_PIO_RETRY;

  		ide_dma_on(drive);

  	}

  	return blk_end_request(rq, error, nr_bytes);

  }

  EXPORT_SYMBOL_GPL(ide_end_rq);

  void ide_complete_cmd(ide_drive_t *drive, struct ide_cmd *cmd, u8 stat, u8 err)

  {

  	const struct ide_tp_ops *tp_ops = drive->hwif->tp_ops;

  	struct ide_taskfile *tf = &cmd->tf;
  	struct request *rq = cmd->rq;

  	u8 tf_cmd = tf->command;

  
  	tf->error = err;
  	tf->status = stat;

  	if (cmd->ftf_flags & IDE_FTFLAG_IN_DATA) {
  		u8 data[2];
  
  		tp_ops->input_data(drive, cmd, data, 2);

  		cmd->tf.data  = data[0];
  		cmd->hob.data = data[1];

  	}

  	ide_tf_readback(drive, cmd);

  	if ((cmd->tf_flags & IDE_TFLAG_CUSTOM_HANDLER) &&
  	    tf_cmd == ATA_CMD_IDLEIMMEDIATE) {
  		if (tf->lbal != 0xc4) {
  			printk(KERN_ERR "%s: head unload failed!
  ",
  			       drive->name);

  			ide_tf_dump(drive->name, cmd);

  		} else
  			drive->dev_flags |= IDE_DFLAG_PARKED;
  	}

  	if (rq && rq->cmd_type == REQ_TYPE_ATA_TASKFILE) {
  		struct ide_cmd *orig_cmd = rq->special;

  		if (cmd->tf_flags & IDE_TFLAG_DYN)
  			kfree(orig_cmd);
  		else
  			memcpy(orig_cmd, cmd, sizeof(*cmd));
  	}

  }

  int ide_complete_rq(ide_drive_t *drive, int error, unsigned int nr_bytes)

  {

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

  	int rc;

  	/*
  	 * if failfast is set on a request, override number of sectors
  	 * and complete the whole request right now
  	 */
  	if (blk_noretry_request(rq) && error <= 0)

  		nr_bytes = blk_rq_sectors(rq) << 9;

  	rc = ide_end_rq(drive, rq, error, nr_bytes);

  	if (rc == 0)
  		hwif->rq = NULL;

  	return rc;

  }

  EXPORT_SYMBOL(ide_complete_rq);

  void ide_kill_rq(ide_drive_t *drive, struct request *rq)

  {

  	u8 drv_req = (rq->cmd_type == REQ_TYPE_SPECIAL) && rq->rq_disk;

  	u8 media = drive->media;

  	drive->failed_pc = NULL;

  	if ((media == ide_floppy || media == ide_tape) && drv_req) {
  		rq->errors = 0;

  	} else {
  		if (media == ide_tape)
  			rq->errors = IDE_DRV_ERROR_GENERAL;

  		else if (rq->cmd_type != REQ_TYPE_FS && rq->errors == 0)

  			rq->errors = -EIO;

  	}

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

  }

  static void ide_tf_set_specify_cmd(ide_drive_t *drive, struct ide_taskfile *tf)

  {

  	tf->nsect   = drive->sect;
  	tf->lbal    = drive->sect;
  	tf->lbam    = drive->cyl;
  	tf->lbah    = drive->cyl >> 8;

  	tf->device  = (drive->head - 1) | drive->select;

  	tf->command = ATA_CMD_INIT_DEV_PARAMS;

  }

  static void ide_tf_set_restore_cmd(ide_drive_t *drive, struct ide_taskfile *tf)

  {

  	tf->nsect   = drive->sect;

  	tf->command = ATA_CMD_RESTORE;

  }

  static void ide_tf_set_setmult_cmd(ide_drive_t *drive, struct ide_taskfile *tf)

  {

  	tf->nsect   = drive->mult_req;

  	tf->command = ATA_CMD_SET_MULTI;

  }

  /**
   *	do_special		-	issue some special commands
   *	@drive: drive the command is for
   *
   *	do_special() is used to issue ATA_CMD_INIT_DEV_PARAMS,
   *	ATA_CMD_RESTORE and ATA_CMD_SET_MULTI commands to a drive.
   */
  
  static ide_startstop_t do_special(ide_drive_t *drive)

  {

  	struct ide_cmd cmd;

  #ifdef DEBUG

  	printk(KERN_DEBUG "%s: %s: 0x%02x
  ", drive->name, __func__,
  		drive->special_flags);

  #endif
  	if (drive->media != ide_disk) {

  		drive->special_flags = 0;

  		drive->mult_req = 0;
  		return ide_stopped;
  	}

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

  	cmd.protocol = ATA_PROT_NODATA;

  	if (drive->special_flags & IDE_SFLAG_SET_GEOMETRY) {
  		drive->special_flags &= ~IDE_SFLAG_SET_GEOMETRY;

  		ide_tf_set_specify_cmd(drive, &cmd.tf);

  	} else if (drive->special_flags & IDE_SFLAG_RECALIBRATE) {
  		drive->special_flags &= ~IDE_SFLAG_RECALIBRATE;

  		ide_tf_set_restore_cmd(drive, &cmd.tf);

  	} else if (drive->special_flags & IDE_SFLAG_SET_MULTMODE) {
  		drive->special_flags &= ~IDE_SFLAG_SET_MULTMODE;

  		ide_tf_set_setmult_cmd(drive, &cmd.tf);

  	} else
  		BUG();

  	cmd.valid.out.tf = IDE_VALID_OUT_TF | IDE_VALID_DEVICE;
  	cmd.valid.in.tf  = IDE_VALID_IN_TF  | IDE_VALID_DEVICE;
  	cmd.tf_flags = IDE_TFLAG_CUSTOM_HANDLER;

  	do_rw_taskfile(drive, &cmd);

  
  	return ide_started;
  }

  void ide_map_sg(ide_drive_t *drive, struct ide_cmd *cmd)

  {
  	ide_hwif_t *hwif = drive->hwif;
  	struct scatterlist *sg = hwif->sg_table;

  	struct request *rq = cmd->rq;

  	cmd->sg_nents = blk_rq_map_sg(drive->queue, rq, sg);

  }

  EXPORT_SYMBOL_GPL(ide_map_sg);

  void ide_init_sg_cmd(struct ide_cmd *cmd, unsigned int nr_bytes)

  {

  	cmd->nbytes = cmd->nleft = nr_bytes;

  	cmd->cursg_ofs = 0;
  	cmd->cursg = NULL;

  }

  EXPORT_SYMBOL_GPL(ide_init_sg_cmd);
  
  /**
   *	execute_drive_command	-	issue special drive command

   *	@drive: the drive to issue the command on

   *	@rq: the request structure holding the command
   *
   *	execute_drive_cmd() issues a special drive command,  usually 
   *	initiated by ioctl() from the external hdparm program. The
   *	command can be a drive command, drive task or taskfile 
   *	operation. Weirdly you can call it with NULL to wait for
   *	all commands to finish. Don't do this as that is due to change
   */
  
  static ide_startstop_t execute_drive_cmd (ide_drive_t *drive,
  		struct request *rq)
  {

  	struct ide_cmd *cmd = rq->special;

  	if (cmd) {

  		if (cmd->protocol == ATA_PROT_PIO) {

  			ide_init_sg_cmd(cmd, blk_rq_sectors(rq) << 9);

  			ide_map_sg(drive, cmd);

  		}

  		return do_rw_taskfile(drive, cmd);

  	}

   	/*
   	 * NULL is actually a valid way of waiting for
   	 * all current requests to be flushed from the queue.
   	 */
  #ifdef DEBUG
   	printk("%s: DRIVE_CMD (null)
  ", drive->name);
  #endif

  	rq->errors = 0;

  	ide_complete_rq(drive, 0, blk_rq_bytes(rq));

   	return ide_stopped;

  }

  static ide_startstop_t ide_special_rq(ide_drive_t *drive, struct request *rq)
  {

  	u8 cmd = rq->cmd[0];

  	switch (cmd) {

  	case REQ_PARK_HEADS:
  	case REQ_UNPARK_HEADS:
  		return ide_do_park_unpark(drive, rq);

  	case REQ_DEVSET_EXEC:

  		return ide_do_devset(drive, rq);

  	case REQ_DRIVE_RESET:
  		return ide_do_reset(drive);
  	default:

  		BUG();

  	}
  }

  /**
   *	start_request	-	start of I/O and command issuing for IDE
   *
   *	start_request() initiates handling of a new I/O request. It

   *	accepts commands and I/O (read/write) requests.

   *
   *	FIXME: this function needs a rename
   */
   
  static ide_startstop_t start_request (ide_drive_t *drive, struct request *rq)
  {
  	ide_startstop_t startstop;

  	BUG_ON(!(rq->cmd_flags & REQ_STARTED));

  
  #ifdef DEBUG
  	printk("%s: start_request: current=0x%08lx
  ",

  		drive->hwif->name, (unsigned long) rq);

  #endif
  
  	/* bail early if we've exceeded max_failures */
  	if (drive->max_failures && (drive->failures > drive->max_failures)) {

  		rq->cmd_flags |= REQ_FAILED;

  		goto kill_rq;
  	}

  	if (blk_pm_request(rq))
  		ide_check_pm_state(drive, rq);

  	drive->hwif->tp_ops->dev_select(drive);

  	if (ide_wait_stat(&startstop, drive, drive->ready_stat,
  			  ATA_BUSY | ATA_DRQ, WAIT_READY)) {

  		printk(KERN_ERR "%s: drive not ready for command
  ", drive->name);
  		return startstop;
  	}

  
  	if (drive->special_flags == 0) {

  		struct ide_driver *drv;

  		/*
  		 * We reset the drive so we need to issue a SETFEATURES.
  		 * Do it _after_ do_special() restored device parameters.
  		 */
  		if (drive->current_speed == 0xff)
  			ide_config_drive_speed(drive, drive->desired_speed);

  		if (rq->cmd_type == REQ_TYPE_ATA_TASKFILE)

  			return execute_drive_cmd(drive, rq);
  		else if (blk_pm_request(rq)) {

  			struct request_pm_state *pm = rq->special;

  #ifdef DEBUG_PM
  			printk("%s: start_power_step(step: %d)
  ",

  				drive->name, pm->pm_step);

  #endif
  			startstop = ide_start_power_step(drive, rq);
  			if (startstop == ide_stopped &&

  			    pm->pm_step == IDE_PM_COMPLETED)

  				ide_complete_pm_rq(drive, rq);

  			return startstop;

  		} else if (!rq->rq_disk && rq->cmd_type == REQ_TYPE_SPECIAL)

  			/*
  			 * TODO: Once all ULDs have been modified to
  			 * check for specific op codes rather than
  			 * blindly accepting any special request, the
  			 * check for ->rq_disk above may be replaced
  			 * by a more suitable mechanism or even
  			 * dropped entirely.
  			 */
  			return ide_special_rq(drive, rq);

  		drv = *(struct ide_driver **)rq->rq_disk->private_data;

  		return drv->do_request(drive, rq, blk_rq_pos(rq));

  	}
  	return do_special(drive);
  kill_rq:
  	ide_kill_rq(drive, rq);
  	return ide_stopped;
  }
  
  /**
   *	ide_stall_queue		-	pause an IDE device
   *	@drive: drive to stall
   *	@timeout: time to stall for (jiffies)
   *
   *	ide_stall_queue() can be used by a drive to give excess bandwidth back

   *	to the port by sleeping for timeout jiffies.

   */
   
  void ide_stall_queue (ide_drive_t *drive, unsigned long timeout)
  {
  	if (timeout > WAIT_WORSTCASE)
  		timeout = WAIT_WORSTCASE;
  	drive->sleep = timeout + jiffies;

  	drive->dev_flags |= IDE_DFLAG_SLEEPING;

  }

  EXPORT_SYMBOL(ide_stall_queue);

  static inline int ide_lock_port(ide_hwif_t *hwif)
  {
  	if (hwif->busy)
  		return 1;
  
  	hwif->busy = 1;
  
  	return 0;
  }
  
  static inline void ide_unlock_port(ide_hwif_t *hwif)
  {
  	hwif->busy = 0;
  }
  
  static inline int ide_lock_host(struct ide_host *host, ide_hwif_t *hwif)
  {
  	int rc = 0;
  
  	if (host->host_flags & IDE_HFLAG_SERIALIZE) {
  		rc = test_and_set_bit_lock(IDE_HOST_BUSY, &host->host_busy);
  		if (rc == 0) {

  			if (host->get_lock)
  				host->get_lock(ide_intr, hwif);

  		}
  	}
  	return rc;
  }
  
  static inline void ide_unlock_host(struct ide_host *host)
  {
  	if (host->host_flags & IDE_HFLAG_SERIALIZE) {

  		if (host->release_lock)
  			host->release_lock();

  		clear_bit_unlock(IDE_HOST_BUSY, &host->host_busy);
  	}
  }

  static void __ide_requeue_and_plug(struct request_queue *q, struct request *rq)
  {
  	if (rq)
  		blk_requeue_request(q, rq);
  	if (rq || blk_peek_request(q)) {
  		/* Use 3ms as that was the old plug delay */
  		blk_delay_queue(q, 3);
  	}
  }
  
  void ide_requeue_and_plug(ide_drive_t *drive, struct request *rq)
  {
  	struct request_queue *q = drive->queue;
  	unsigned long flags;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	__ide_requeue_and_plug(q, rq);
  	spin_unlock_irqrestore(q->queue_lock, flags);
  }

  /*

   * Issue a new request to a device.

   */

  void do_ide_request(struct request_queue *q)

  {

  	ide_drive_t	*drive = q->queuedata;
  	ide_hwif_t	*hwif = drive->hwif;

  	struct ide_host *host = hwif->host;

  	struct request	*rq = NULL;

  	ide_startstop_t	startstop;

  	unsigned long queue_run_ms = 3; /* old plug delay */

  	spin_unlock_irq(q->queue_lock);

  	/* HLD do_request() callback might sleep, make sure it's okay */
  	might_sleep();

  	if (ide_lock_host(host, hwif))
  		goto plug_device_2;

  	spin_lock_irq(&hwif->lock);

  	if (!ide_lock_port(hwif)) {

  		ide_hwif_t *prev_port;

  
  		WARN_ON_ONCE(hwif->rq);

  repeat:

  		prev_port = hwif->host->cur_port;

  		if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
  		    time_after(drive->sleep, jiffies)) {

  			unsigned long left = jiffies - drive->sleep;
  
  			queue_run_ms = jiffies_to_msecs(left + 1);

  			ide_unlock_port(hwif);
  			goto plug_device;

  		}

  		if ((hwif->host->host_flags & IDE_HFLAG_SERIALIZE) &&
  		    hwif != prev_port) {

  			ide_drive_t *cur_dev =
  				prev_port ? prev_port->cur_dev : NULL;

  			/*

  			 * set nIEN for previous port, drives in the

  			 * quirk list may not like intr setups/cleanups

  			 */

  			if (cur_dev &&
  			    (cur_dev->dev_flags & IDE_DFLAG_NIEN_QUIRK) == 0)

  				prev_port->tp_ops->write_devctl(prev_port,
  								ATA_NIEN |
  								ATA_DEVCTL_OBS);

  
  			hwif->host->cur_port = hwif;

  		}

  		hwif->cur_dev = drive;

  		drive->dev_flags &= ~(IDE_DFLAG_SLEEPING | IDE_DFLAG_PARKED);

  		spin_unlock_irq(&hwif->lock);
  		spin_lock_irq(q->queue_lock);
  		/*
  		 * we know that the queue isn't empty, but this can happen
  		 * if the q->prep_rq_fn() decides to kill a request
  		 */
  		if (!rq)

  			rq = blk_fetch_request(drive->queue);

  		spin_unlock_irq(q->queue_lock);
  		spin_lock_irq(&hwif->lock);
  
  		if (!rq) {
  			ide_unlock_port(hwif);
  			goto out;

  		}
  
  		/*
  		 * Sanity: don't accept a request that isn't a PM request

  		 * if we are currently power managed. This is very important as
  		 * blk_stop_queue() doesn't prevent the blk_fetch_request()
  		 * above to return us whatever is in the queue. Since we call
  		 * ide_do_request() ourselves, we end up taking requests while
  		 * the queue is blocked...
  		 * 
  		 * We let requests forced at head of queue with ide-preempt
  		 * though. I hope that doesn't happen too much, hopefully not
  		 * unless the subdriver triggers such a thing in its own PM
  		 * state machine.

  		 */

  		if ((drive->dev_flags & IDE_DFLAG_BLOCKED) &&
  		    blk_pm_request(rq) == 0 &&
  		    (rq->cmd_flags & REQ_PREEMPT) == 0) {
  			/* there should be no pending command at this point */
  			ide_unlock_port(hwif);
  			goto plug_device;
  		}

  		hwif->rq = rq;

  		spin_unlock_irq(&hwif->lock);

  		startstop = start_request(drive, rq);

  		spin_lock_irq(&hwif->lock);

  		if (startstop == ide_stopped) {
  			rq = hwif->rq;
  			hwif->rq = NULL;

  			goto repeat;

  		}

  	} else
  		goto plug_device;
  out:

  	spin_unlock_irq(&hwif->lock);

  	if (rq == NULL)
  		ide_unlock_host(host);

  	spin_lock_irq(q->queue_lock);

  	return;

  plug_device:

  	spin_unlock_irq(&hwif->lock);

  	ide_unlock_host(host);
  plug_device_2:

  	spin_lock_irq(q->queue_lock);

  	__ide_requeue_and_plug(q, rq);

  }

  static int drive_is_ready(ide_drive_t *drive)
  {
  	ide_hwif_t *hwif = drive->hwif;
  	u8 stat = 0;
  
  	if (drive->waiting_for_dma)
  		return hwif->dma_ops->dma_test_irq(drive);
  
  	if (hwif->io_ports.ctl_addr &&
  	    (hwif->host_flags & IDE_HFLAG_BROKEN_ALTSTATUS) == 0)
  		stat = hwif->tp_ops->read_altstatus(hwif);
  	else
  		/* Note: this may clear a pending IRQ!! */
  		stat = hwif->tp_ops->read_status(hwif);
  
  	if (stat & ATA_BUSY)
  		/* drive busy: definitely not interrupting */
  		return 0;
  
  	/* drive ready: *might* be interrupting */
  	return 1;
  }

  /**
   *	ide_timer_expiry	-	handle lack of an IDE interrupt

   *	@data: timer callback magic (hwif)

   *
   *	An IDE command has timed out before the expected drive return
   *	occurred. At this point we attempt to clean up the current
   *	mess. If the current handler includes an expiry handler then
   *	we invoke the expiry handler, and providing it is happy the
   *	work is done. If that fails we apply generic recovery rules
   *	invoking the handler and checking the drive DMA status. We
   *	have an excessively incestuous relationship with the DMA
   *	logic that wants cleaning up.
   */
   
  void ide_timer_expiry (unsigned long data)
  {

  	ide_hwif_t	*hwif = (ide_hwif_t *)data;

  	ide_drive_t	*uninitialized_var(drive);

  	ide_handler_t	*handler;

  	unsigned long	flags;

  	int		wait = -1;

  	int		plug_device = 0;

  	struct request	*uninitialized_var(rq_in_flight);

  	spin_lock_irqsave(&hwif->lock, flags);
  
  	handler = hwif->handler;

  	if (handler == NULL || hwif->req_gen != hwif->req_gen_timer) {

  		/*
  		 * Either a marginal timeout occurred
  		 * (got the interrupt just as timer expired),
  		 * or we were "sleeping" to give other devices a chance.
  		 * Either way, we don't really want to complain about anything.
  		 */

  	} else {

  		ide_expiry_t *expiry = hwif->expiry;
  		ide_startstop_t startstop = ide_stopped;

  		drive = hwif->cur_dev;

  
  		if (expiry) {
  			wait = expiry(drive);
  			if (wait > 0) { /* continue */
  				/* reset timer */
  				hwif->timer.expires = jiffies + wait;
  				hwif->req_gen_timer = hwif->req_gen;
  				add_timer(&hwif->timer);
  				spin_unlock_irqrestore(&hwif->lock, flags);
  				return;

  			}

  		}

  		hwif->handler = NULL;

  		hwif->expiry = NULL;

  		/*
  		 * We need to simulate a real interrupt when invoking
  		 * the handler() function, which means we need to
  		 * globally mask the specific IRQ:
  		 */
  		spin_unlock(&hwif->lock);
  		/* disable_irq_nosync ?? */
  		disable_irq(hwif->irq);
  		/* local CPU only, as if we were handling an interrupt */
  		local_irq_disable();
  		if (hwif->polling) {
  			startstop = handler(drive);
  		} else if (drive_is_ready(drive)) {
  			if (drive->waiting_for_dma)
  				hwif->dma_ops->dma_lost_irq(drive);

  			if (hwif->port_ops && hwif->port_ops->clear_irq)
  				hwif->port_ops->clear_irq(drive);

  			printk(KERN_WARNING "%s: lost interrupt
  ",
  				drive->name);
  			startstop = handler(drive);
  		} else {
  			if (drive->waiting_for_dma)
  				startstop = ide_dma_timeout_retry(drive, wait);
  			else
  				startstop = ide_error(drive, "irq timeout",
  					hwif->tp_ops->read_status(hwif));
  		}
  		spin_lock_irq(&hwif->lock);
  		enable_irq(hwif->irq);

  		if (startstop == ide_stopped && hwif->polling == 0) {

  			rq_in_flight = hwif->rq;
  			hwif->rq = NULL;

  			ide_unlock_port(hwif);
  			plug_device = 1;
  		}

  	}

  	spin_unlock_irqrestore(&hwif->lock, flags);

  	if (plug_device) {
  		ide_unlock_host(hwif->host);

  		ide_requeue_and_plug(drive, rq_in_flight);

  	}

  }
  
  /**
   *	unexpected_intr		-	handle an unexpected IDE interrupt
   *	@irq: interrupt line

   *	@hwif: port being processed

   *
   *	There's nothing really useful we can do with an unexpected interrupt,
   *	other than reading the status register (to clear it), and logging it.
   *	There should be no way that an irq can happen before we're ready for it,
   *	so we needn't worry much about losing an "important" interrupt here.
   *
   *	On laptops (and "green" PCs), an unexpected interrupt occurs whenever
   *	the drive enters "idle", "standby", or "sleep" mode, so if the status
   *	looks "good", we just ignore the interrupt completely.
   *
   *	This routine assumes __cli() is in effect when called.
   *
   *	If an unexpected interrupt happens on irq15 while we are handling irq14
   *	and if the two interfaces are "serialized" (CMD640), then it looks like
   *	we could screw up by interfering with a new request being set up for 
   *	irq15.
   *
   *	In reality, this is a non-issue.  The new command is not sent unless 
   *	the drive is ready to accept one, in which case we know the drive is
   *	not trying to interrupt us.  And ide_set_handler() is always invoked
   *	before completing the issuance of any new drive command, so we will not
   *	be accidentally invoked as a result of any valid command completion
   *	interrupt.

   */

  
  static void unexpected_intr(int irq, ide_hwif_t *hwif)

  {

  	u8 stat = hwif->tp_ops->read_status(hwif);
  
  	if (!OK_STAT(stat, ATA_DRDY, BAD_STAT)) {
  		/* Try to not flood the console with msgs */
  		static unsigned long last_msgtime, count;
  		++count;
  
  		if (time_after(jiffies, last_msgtime + HZ)) {
  			last_msgtime = jiffies;
  			printk(KERN_ERR "%s: unexpected interrupt, "
  				"status=0x%02x, count=%ld
  ",
  				hwif->name, stat, count);

  		}

  	}

  }
  
  /**
   *	ide_intr	-	default IDE interrupt handler
   *	@irq: interrupt number

   *	@dev_id: hwif

   *	@regs: unused weirdness from the kernel irq layer
   *
   *	This is the default IRQ handler for the IDE layer. You should
   *	not need to override it. If you do be aware it is subtle in
   *	places
   *

   *	hwif is the interface in the group currently performing

   *	a command. hwif->cur_dev is the drive and hwif->handler is

   *	the IRQ handler to call. As we issue a command the handlers
   *	step through multiple states, reassigning the handler to the
   *	next step in the process. Unlike a smart SCSI controller IDE
   *	expects the main processor to sequence the various transfer
   *	stages. We also manage a poll timer to catch up with most
   *	timeout situations. There are still a few where the handlers
   *	don't ever decide to give up.
   *
   *	The handler eventually returns ide_stopped to indicate the
   *	request completed. At this point we issue the next request

   *	on the port and the process begins again.

   */

  irqreturn_t ide_intr (int irq, void *dev_id)

  {

  	ide_hwif_t *hwif = (ide_hwif_t *)dev_id;

  	struct ide_host *host = hwif->host;

  	ide_drive_t *uninitialized_var(drive);

  	ide_handler_t *handler;

  	unsigned long flags;

  	ide_startstop_t startstop;

  	irqreturn_t irq_ret = IRQ_NONE;

  	int plug_device = 0;

  	struct request *uninitialized_var(rq_in_flight);

  	if (host->host_flags & IDE_HFLAG_SERIALIZE) {
  		if (hwif != host->cur_port)

  			goto out_early;
  	}

  	spin_lock_irqsave(&hwif->lock, flags);

  	if (hwif->port_ops && hwif->port_ops->test_irq &&
  	    hwif->port_ops->test_irq(hwif) == 0)

  		goto out;

  	handler = hwif->handler;
  
  	if (handler == NULL || hwif->polling) {

  		/*
  		 * Not expecting an interrupt from this drive.
  		 * That means this could be:
  		 *	(1) an interrupt from another PCI device
  		 *	sharing the same PCI INT# as us.
  		 * or	(2) a drive just entered sleep or standby mode,
  		 *	and is interrupting to let us know.
  		 * or	(3) a spurious interrupt of unknown origin.
  		 *
  		 * For PCI, we cannot tell the difference,
  		 * so in that case we just ignore it and hope it goes away.

  		 */

  		if ((host->irq_flags & IRQF_SHARED) == 0) {

  			/*
  			 * Probably not a shared PCI interrupt,
  			 * so we can safely try to do something about it:
  			 */

  			unexpected_intr(irq, hwif);

  		} else {
  			/*
  			 * Whack the status register, just in case
  			 * we have a leftover pending IRQ.
  			 */

  			(void)hwif->tp_ops->read_status(hwif);

  		}

  		goto out;

  	}

  	drive = hwif->cur_dev;

  
  	if (!drive_is_ready(drive))

  		/*
  		 * This happens regularly when we share a PCI IRQ with
  		 * another device.  Unfortunately, it can also happen
  		 * with some buggy drives that trigger the IRQ before
  		 * their status register is up to date.  Hopefully we have
  		 * enough advance overhead that the latter isn't a problem.
  		 */

  		goto out;

  	hwif->handler = NULL;

  	hwif->expiry = NULL;

  	hwif->req_gen++;
  	del_timer(&hwif->timer);
  	spin_unlock(&hwif->lock);

  	if (hwif->port_ops && hwif->port_ops->clear_irq)
  		hwif->port_ops->clear_irq(drive);

  	if (drive->dev_flags & IDE_DFLAG_UNMASK)

  		local_irq_enable_in_hardirq();

  	/* service this interrupt, may set handler for next interrupt */
  	startstop = handler(drive);

  	spin_lock_irq(&hwif->lock);

  	/*
  	 * Note that handler() may have set things up for another
  	 * interrupt to occur soon, but it cannot happen until
  	 * we exit from this routine, because it will be the
  	 * same irq as is currently being serviced here, and Linux
  	 * won't allow another of the same (on any CPU) until we return.
  	 */

  	if (startstop == ide_stopped && hwif->polling == 0) {

  		BUG_ON(hwif->handler);

  		rq_in_flight = hwif->rq;
  		hwif->rq = NULL;

  		ide_unlock_port(hwif);
  		plug_device = 1;

  	}

  	irq_ret = IRQ_HANDLED;
  out:

  	spin_unlock_irqrestore(&hwif->lock, flags);

  out_early:

  	if (plug_device) {
  		ide_unlock_host(hwif->host);

  		ide_requeue_and_plug(drive, rq_in_flight);

  	}

  	return irq_ret;

  }

  EXPORT_SYMBOL_GPL(ide_intr);

  void ide_pad_transfer(ide_drive_t *drive, int write, int len)
  {
  	ide_hwif_t *hwif = drive->hwif;
  	u8 buf[4] = { 0 };
  
  	while (len > 0) {
  		if (write)

  			hwif->tp_ops->output_data(drive, NULL, buf, min(4, len));

  		else

  			hwif->tp_ops->input_data(drive, NULL, buf, min(4, len));

  		len -= 4;
  	}
  }
  EXPORT_SYMBOL_GPL(ide_pad_transfer);