/*

   * Interface to Linux block layer for MTD 'translation layers'.

   *

   * Copyright © 2003-2010 David Woodhouse <dwmw2@infradead.org>
   *
   * 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 of the License, 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

   *
   */
  
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/list.h>
  #include <linux/fs.h>
  #include <linux/mtd/blktrans.h>
  #include <linux/mtd/mtd.h>
  #include <linux/blkdev.h>
  #include <linux/blkpg.h>
  #include <linux/spinlock.h>
  #include <linux/hdreg.h>
  #include <linux/init.h>

  #include <linux/mutex.h>

  #include <linux/kthread.h>

  #include <asm/uaccess.h>

  #include "mtdcore.h"

  static LIST_HEAD(blktrans_majors);

  static DEFINE_MUTEX(blktrans_ref_mutex);

  static void blktrans_dev_release(struct kref *kref)

  {
  	struct mtd_blktrans_dev *dev =
  		container_of(kref, struct mtd_blktrans_dev, ref);
  
  	dev->disk->private_data = NULL;

  	blk_cleanup_queue(dev->rq);

  	put_disk(dev->disk);
  	list_del(&dev->list);
  	kfree(dev);
  }
  
  static struct mtd_blktrans_dev *blktrans_dev_get(struct gendisk *disk)
  {
  	struct mtd_blktrans_dev *dev;
  
  	mutex_lock(&blktrans_ref_mutex);
  	dev = disk->private_data;
  
  	if (!dev)
  		goto unlock;
  	kref_get(&dev->ref);
  unlock:
  	mutex_unlock(&blktrans_ref_mutex);
  	return dev;
  }

  static void blktrans_dev_put(struct mtd_blktrans_dev *dev)

  {
  	mutex_lock(&blktrans_ref_mutex);
  	kref_put(&dev->ref, blktrans_dev_release);
  	mutex_unlock(&blktrans_ref_mutex);
  }

  
  static int do_blktrans_request(struct mtd_blktrans_ops *tr,
  			       struct mtd_blktrans_dev *dev,
  			       struct request *req)
  {
  	unsigned long block, nsect;
  	char *buf;

  	block = blk_rq_pos(req) << 9 >> tr->blkshift;

  	nsect = blk_rq_cur_bytes(req) >> tr->blkshift;

  	buf = req->buffer;

  	if (req->cmd_type != REQ_TYPE_FS)

  		return -EIO;

  	if (blk_rq_pos(req) + blk_rq_cur_sectors(req) >
  	    get_capacity(req->rq_disk))

  		return -EIO;

  	if (req->cmd_flags & REQ_DISCARD)

  		return tr->discard(dev, block, nsect);

  	switch(rq_data_dir(req)) {
  	case READ:

  		for (; nsect > 0; nsect--, block++, buf += tr->blksize)

  			if (tr->readsect(dev, block, buf))

  				return -EIO;

  		rq_flush_dcache_pages(req);

  		return 0;

  	case WRITE:
  		if (!tr->writesect)

  			return -EIO;

  		rq_flush_dcache_pages(req);

  		for (; nsect > 0; nsect--, block++, buf += tr->blksize)

  			if (tr->writesect(dev, block, buf))

  				return -EIO;
  		return 0;

  	default:

  		printk(KERN_NOTICE "Unknown request %u
  ", rq_data_dir(req));

  		return -EIO;

  	}
  }

  int mtd_blktrans_cease_background(struct mtd_blktrans_dev *dev)
  {
  	if (kthread_should_stop())
  		return 1;

  	return dev->bg_stop;

  }
  EXPORT_SYMBOL_GPL(mtd_blktrans_cease_background);

  static int mtd_blktrans_thread(void *arg)
  {

  	struct mtd_blktrans_dev *dev = arg;

  	struct mtd_blktrans_ops *tr = dev->tr;

  	struct request_queue *rq = dev->rq;

  	struct request *req = NULL;

  	int background_done = 0;

  	spin_lock_irq(rq->queue_lock);

  	while (!kthread_should_stop()) {

  		int res;

  		dev->bg_stop = false;

  		if (!req && !(req = blk_fetch_request(rq))) {

  			if (tr->background && !background_done) {
  				spin_unlock_irq(rq->queue_lock);
  				mutex_lock(&dev->lock);
  				tr->background(dev);
  				mutex_unlock(&dev->lock);
  				spin_lock_irq(rq->queue_lock);
  				/*
  				 * Do background processing just once per idle
  				 * period.
  				 */

  				background_done = !dev->bg_stop;

  				continue;
  			}

  			set_current_state(TASK_INTERRUPTIBLE);

  
  			if (kthread_should_stop())
  				set_current_state(TASK_RUNNING);

  			spin_unlock_irq(rq->queue_lock);

  			schedule();

  			spin_lock_irq(rq->queue_lock);

  			continue;
  		}

  		spin_unlock_irq(rq->queue_lock);

  		mutex_lock(&dev->lock);

  		res = do_blktrans_request(dev->tr, dev, req);

  		mutex_unlock(&dev->lock);

  
  		spin_lock_irq(rq->queue_lock);

  		if (!__blk_end_request_cur(req, res))
  			req = NULL;

  
  		background_done = 0;

  	}

  
  	if (req)
  		__blk_end_request_all(req, -EIO);

  	spin_unlock_irq(rq->queue_lock);

  	return 0;

  }
  
  static void mtd_blktrans_request(struct request_queue *rq)
  {

  	struct mtd_blktrans_dev *dev;
  	struct request *req = NULL;
  
  	dev = rq->queuedata;

  	if (!dev)
  		while ((req = blk_fetch_request(rq)) != NULL)
  			__blk_end_request_all(req, -ENODEV);

  	else {
  		dev->bg_stop = true;

  		wake_up_process(dev->thread);

  	}

  }

  static int blktrans_open(struct block_device *bdev, fmode_t mode)

  {

  	struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);

  	int ret = 0;

  
  	if (!dev)

  		return -ERESTARTSYS; /* FIXME: busy loop! -arnd*/

  
  	mutex_lock(&dev->lock);

  	if (dev->open++)

  		goto unlock;

  	kref_get(&dev->ref);
  	__module_get(dev->tr->owner);

  	if (!dev->mtd)
  		goto unlock;
  
  	if (dev->tr->open) {
  		ret = dev->tr->open(dev);
  		if (ret)
  			goto error_put;

  	}

  	ret = __get_mtd_device(dev->mtd);
  	if (ret)
  		goto error_release;

  unlock:
  	mutex_unlock(&dev->lock);
  	blktrans_dev_put(dev);

  	return ret;

  
  error_release:
  	if (dev->tr->release)
  		dev->tr->release(dev);
  error_put:
  	module_put(dev->tr->owner);
  	kref_put(&dev->ref, blktrans_dev_release);
  	mutex_unlock(&dev->lock);
  	blktrans_dev_put(dev);
  	return ret;

  }

  static int blktrans_release(struct gendisk *disk, fmode_t mode)

  {

  	struct mtd_blktrans_dev *dev = blktrans_dev_get(disk);

  	int ret = 0;

  	if (!dev)
  		return ret;

  	mutex_lock(&dev->lock);

  	if (--dev->open)

  		goto unlock;

  	kref_put(&dev->ref, blktrans_dev_release);
  	module_put(dev->tr->owner);
  
  	if (dev->mtd) {
  		ret = dev->tr->release ? dev->tr->release(dev) : 0;
  		__put_mtd_device(dev->mtd);
  	}

  unlock:
  	mutex_unlock(&dev->lock);
  	blktrans_dev_put(dev);

  	return ret;
  }

  static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
  {

  	struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
  	int ret = -ENXIO;
  
  	if (!dev)
  		return ret;
  
  	mutex_lock(&dev->lock);

  	if (!dev->mtd)
  		goto unlock;
  
  	ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : 0;
  unlock:
  	mutex_unlock(&dev->lock);
  	blktrans_dev_put(dev);
  	return ret;

  }

  static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,

  			      unsigned int cmd, unsigned long arg)
  {

  	struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
  	int ret = -ENXIO;
  
  	if (!dev)
  		return ret;
  
  	mutex_lock(&dev->lock);
  
  	if (!dev->mtd)
  		goto unlock;

  
  	switch (cmd) {
  	case BLKFLSBUF:

  		ret = dev->tr->flush ? dev->tr->flush(dev) : 0;

  		break;

  	default:

  		ret = -ENOTTY;

  	}

  unlock:
  	mutex_unlock(&dev->lock);
  	blktrans_dev_put(dev);
  	return ret;

  }

  static const struct block_device_operations mtd_blktrans_ops = {

  	.owner		= THIS_MODULE,

  	.open		= blktrans_open,
  	.release	= blktrans_release,

  	.ioctl		= blktrans_ioctl,

  	.getgeo		= blktrans_getgeo,

  };
  
  int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
  {
  	struct mtd_blktrans_ops *tr = new->tr;

  	struct mtd_blktrans_dev *d;

  	int last_devnum = -1;
  	struct gendisk *gd;

  	int ret;

  	if (mutex_trylock(&mtd_table_mutex)) {

  		mutex_unlock(&mtd_table_mutex);

  		BUG();
  	}

  	mutex_lock(&blktrans_ref_mutex);

  	list_for_each_entry(d, &tr->devs, list) {

  		if (new->devnum == -1) {
  			/* Use first free number */
  			if (d->devnum != last_devnum+1) {
  				/* Found a free devnum. Plug it in here */
  				new->devnum = last_devnum+1;
  				list_add_tail(&new->list, &d->list);
  				goto added;
  			}
  		} else if (d->devnum == new->devnum) {
  			/* Required number taken */

  			mutex_unlock(&blktrans_ref_mutex);

  			return -EBUSY;
  		} else if (d->devnum > new->devnum) {
  			/* Required number was free */
  			list_add_tail(&new->list, &d->list);
  			goto added;

  		}

  		last_devnum = d->devnum;
  	}

  
  	ret = -EBUSY;

  	if (new->devnum == -1)
  		new->devnum = last_devnum+1;

  	/* Check that the device and any partitions will get valid
  	 * minor numbers and that the disk naming code below can cope
  	 * with this number. */
  	if (new->devnum > (MINORMASK >> tr->part_bits) ||

  	    (tr->part_bits && new->devnum >= 27 * 26)) {
  		mutex_unlock(&blktrans_ref_mutex);

  		goto error1;

  	}

  	list_add_tail(&new->list, &tr->devs);
   added:

  	mutex_unlock(&blktrans_ref_mutex);

  	mutex_init(&new->lock);

  	kref_init(&new->ref);

  	if (!tr->writesect)
  		new->readonly = 1;

  	/* Create gendisk */
  	ret = -ENOMEM;

  	gd = alloc_disk(1 << tr->part_bits);

  
  	if (!gd)
  		goto error2;
  
  	new->disk = gd;
  	gd->private_data = new;

  	gd->major = tr->major;
  	gd->first_minor = (new->devnum) << tr->part_bits;
  	gd->fops = &mtd_blktrans_ops;

  	if (tr->part_bits)
  		if (new->devnum < 26)
  			snprintf(gd->disk_name, sizeof(gd->disk_name),
  				 "%s%c", tr->name, 'a' + new->devnum);
  		else
  			snprintf(gd->disk_name, sizeof(gd->disk_name),
  				 "%s%c%c", tr->name,
  				 'a' - 1 + new->devnum / 26,
  				 'a' + new->devnum % 26);
  	else
  		snprintf(gd->disk_name, sizeof(gd->disk_name),
  			 "%s%d", tr->name, new->devnum);

  	set_capacity(gd, (new->size * tr->blksize) >> 9);

  	/* Create the request queue */
  	spin_lock_init(&new->queue_lock);
  	new->rq = blk_init_queue(mtd_blktrans_request, &new->queue_lock);
  
  	if (!new->rq)
  		goto error3;
  
  	new->rq->queuedata = new;
  	blk_queue_logical_block_size(new->rq, tr->blksize);

  	if (tr->discard) {
  		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, new->rq);
  		new->rq->limits.max_discard_sectors = UINT_MAX;
  	}

  
  	gd->queue = new->rq;
  
  	/* Create processing thread */
  	/* TODO: workqueue ? */
  	new->thread = kthread_run(mtd_blktrans_thread, new,
  			"%s%d", tr->name, new->mtd->index);
  	if (IS_ERR(new->thread)) {
  		ret = PTR_ERR(new->thread);
  		goto error4;
  	}

  	gd->driverfs_dev = &new->mtd->dev;

  
  	if (new->readonly)
  		set_disk_ro(gd, 1);
  
  	add_disk(gd);

  	if (new->disk_attributes) {
  		ret = sysfs_create_group(&disk_to_dev(gd)->kobj,

  					new->disk_attributes);

  		WARN_ON(ret);
  	}

  	return 0;

  error4:
  	blk_cleanup_queue(new->rq);
  error3:
  	put_disk(new->disk);
  error2:
  	list_del(&new->list);
  error1:

  	return ret;

  }
  
  int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
  {

  	unsigned long flags;

  	if (mutex_trylock(&mtd_table_mutex)) {

  		mutex_unlock(&mtd_table_mutex);

  		BUG();
  	}

  	if (old->disk_attributes)
  		sysfs_remove_group(&disk_to_dev(old->disk)->kobj,
  						old->disk_attributes);

  	/* Stop new requests to arrive */
  	del_gendisk(old->disk);

  	/* Stop the thread */
  	kthread_stop(old->thread);

  	/* Kill current requests */
  	spin_lock_irqsave(&old->queue_lock, flags);
  	old->rq->queuedata = NULL;
  	blk_start_queue(old->rq);
  	spin_unlock_irqrestore(&old->queue_lock, flags);

  	/* If the device is currently open, tell trans driver to close it,
  		then put mtd device, and don't touch it again */

  	mutex_lock(&old->lock);

  	if (old->open) {
  		if (old->tr->release)
  			old->tr->release(old);
  		__put_mtd_device(old->mtd);

  	}

  	old->mtd = NULL;
  
  	mutex_unlock(&old->lock);
  	blktrans_dev_put(old);

  	return 0;
  }
  
  static void blktrans_notify_remove(struct mtd_info *mtd)
  {

  	struct mtd_blktrans_ops *tr;
  	struct mtd_blktrans_dev *dev, *next;

  	list_for_each_entry(tr, &blktrans_majors, list)
  		list_for_each_entry_safe(dev, next, &tr->devs, list)

  			if (dev->mtd == mtd)
  				tr->remove_dev(dev);

  }
  
  static void blktrans_notify_add(struct mtd_info *mtd)
  {

  	struct mtd_blktrans_ops *tr;

  
  	if (mtd->type == MTD_ABSENT)
  		return;

  	list_for_each_entry(tr, &blktrans_majors, list)

  		tr->add_mtd(tr, mtd);

  }
  
  static struct mtd_notifier blktrans_notifier = {
  	.add = blktrans_notify_add,
  	.remove = blktrans_notify_remove,
  };

  int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
  {

  	struct mtd_info *mtd;
  	int ret;

  	/* Register the notifier if/when the first device type is

  	   registered, to prevent the link/init ordering from fucking
  	   us over. */
  	if (!blktrans_notifier.list.next)
  		register_mtd_user(&blktrans_notifier);

  	mutex_lock(&mtd_table_mutex);

  
  	ret = register_blkdev(tr->major, tr->name);

  	if (ret < 0) {

  		printk(KERN_WARNING "Unable to register %s block device on major %d: %d
  ",
  		       tr->name, tr->major, ret);

  		mutex_unlock(&mtd_table_mutex);

  		return ret;
  	}

  	if (ret)
  		tr->major = ret;

  	tr->blkshift = ffs(tr->blksize) - 1;

  	INIT_LIST_HEAD(&tr->devs);
  	list_add(&tr->list, &blktrans_majors);

  	mtd_for_each_device(mtd)
  		if (mtd->type != MTD_ABSENT)
  			tr->add_mtd(tr, mtd);

  	mutex_unlock(&mtd_table_mutex);

  	return 0;
  }
  
  int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
  {

  	struct mtd_blktrans_dev *dev, *next;

  	mutex_lock(&mtd_table_mutex);

  	/* Remove it from the list of active majors */
  	list_del(&tr->list);

  	list_for_each_entry_safe(dev, next, &tr->devs, list)

  		tr->remove_dev(dev);

  	unregister_blkdev(tr->major, tr->name);

  	mutex_unlock(&mtd_table_mutex);

  	BUG_ON(!list_empty(&tr->devs));

  	return 0;
  }
  
  static void __exit mtd_blktrans_exit(void)
  {
  	/* No race here -- if someone's currently in register_mtd_blktrans
  	   we're screwed anyway. */
  	if (blktrans_notifier.list.next)
  		unregister_mtd_user(&blktrans_notifier);
  }
  
  module_exit(mtd_blktrans_exit);
  
  EXPORT_SYMBOL_GPL(register_mtd_blktrans);
  EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
  EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
  EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);
  
  MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");