/*

   * $Id: mtd_blkdevs.c,v 1.27 2005/11/07 11:14:20 gleixner Exp $

   *
   * (C) 2003 David Woodhouse <dwmw2@infradead.org>
   *
   * Interface to Linux 2.5 block layer for MTD 'translation layers'.
   *
   */
  
  #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/freezer.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);

  
  struct mtd_blkcore_priv {

  	struct task_struct *thread;

  	struct request_queue *rq;
  	spinlock_t queue_lock;
  };
  
  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 = req->sector << 9 >> tr->blkshift;
  	nsect = req->current_nr_sectors << 9 >> tr->blkshift;

  	buf = req->buffer;

  	if (!blk_fs_request(req))

  		return 0;

  	if (req->sector + req->current_nr_sectors > get_capacity(req->rq_disk))

  		return 0;
  
  	switch(rq_data_dir(req)) {
  	case READ:

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

  			if (tr->readsect(dev, block, buf))
  				return 0;
  		return 1;
  
  	case WRITE:
  		if (!tr->writesect)
  			return 0;

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

  			if (tr->writesect(dev, block, buf))
  				return 0;
  		return 1;
  
  	default:

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

  		return 0;
  	}
  }
  
  static int mtd_blktrans_thread(void *arg)
  {
  	struct mtd_blktrans_ops *tr = arg;
  	struct request_queue *rq = tr->blkcore_priv->rq;
  
  	/* we might get involved when memory gets low, so use PF_MEMALLOC */

  	current->flags |= PF_MEMALLOC;

  	spin_lock_irq(rq->queue_lock);

  	while (!kthread_should_stop()) {

  		struct request *req;
  		struct mtd_blktrans_dev *dev;
  		int res = 0;

  
  		req = elv_next_request(rq);
  
  		if (!req) {

  			set_current_state(TASK_INTERRUPTIBLE);

  			spin_unlock_irq(rq->queue_lock);

  			schedule();

  			spin_lock_irq(rq->queue_lock);

  			continue;
  		}
  
  		dev = req->rq_disk->private_data;
  		tr = dev->tr;
  
  		spin_unlock_irq(rq->queue_lock);

  		mutex_lock(&dev->lock);

  		res = do_blktrans_request(tr, dev, req);

  		mutex_unlock(&dev->lock);

  
  		spin_lock_irq(rq->queue_lock);
  
  		end_request(req, res);
  	}
  	spin_unlock_irq(rq->queue_lock);

  	return 0;

  }
  
  static void mtd_blktrans_request(struct request_queue *rq)
  {
  	struct mtd_blktrans_ops *tr = rq->queuedata;

  	wake_up_process(tr->blkcore_priv->thread);

  }
  
  
  static int blktrans_open(struct inode *i, struct file *f)
  {
  	struct mtd_blktrans_dev *dev;
  	struct mtd_blktrans_ops *tr;
  	int ret = -ENODEV;
  
  	dev = i->i_bdev->bd_disk->private_data;
  	tr = dev->tr;
  
  	if (!try_module_get(dev->mtd->owner))
  		goto out;
  
  	if (!try_module_get(tr->owner))
  		goto out_tr;

  	/* FIXME: Locking. A hot pluggable device can go away

  	   (del_mtd_device can be called for it) without its module
  	   being unloaded. */
  	dev->mtd->usecount++;
  
  	ret = 0;
  	if (tr->open && (ret = tr->open(dev))) {
  		dev->mtd->usecount--;
  		module_put(dev->mtd->owner);
  	out_tr:
  		module_put(tr->owner);
  	}
   out:
  	return ret;
  }
  
  static int blktrans_release(struct inode *i, struct file *f)
  {
  	struct mtd_blktrans_dev *dev;
  	struct mtd_blktrans_ops *tr;
  	int ret = 0;
  
  	dev = i->i_bdev->bd_disk->private_data;
  	tr = dev->tr;
  
  	if (tr->release)
  		ret = tr->release(dev);
  
  	if (!ret) {
  		dev->mtd->usecount--;
  		module_put(dev->mtd->owner);
  		module_put(tr->owner);
  	}
  
  	return ret;
  }

  static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
  {
  	struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
  
  	if (dev->tr->getgeo)
  		return dev->tr->getgeo(dev, geo);
  	return -ENOTTY;
  }

  static int blktrans_ioctl(struct inode *inode, struct file *file,

  			      unsigned int cmd, unsigned long arg)
  {
  	struct mtd_blktrans_dev *dev = inode->i_bdev->bd_disk->private_data;
  	struct mtd_blktrans_ops *tr = dev->tr;
  
  	switch (cmd) {
  	case BLKFLSBUF:
  		if (tr->flush)
  			return tr->flush(dev);
  		/* The core code did the work, we had nothing to do. */
  		return 0;

  	default:
  		return -ENOTTY;
  	}
  }

  static 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 list_head *this;
  	int last_devnum = -1;
  	struct gendisk *gd;

  	if (mutex_trylock(&mtd_table_mutex)) {

  		mutex_unlock(&mtd_table_mutex);

  		BUG();
  	}
  
  	list_for_each(this, &tr->devs) {
  		struct mtd_blktrans_dev *d = list_entry(this, struct mtd_blktrans_dev, 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 */
  			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;
  	}
  	if (new->devnum == -1)
  		new->devnum = last_devnum+1;
  
  	if ((new->devnum << tr->part_bits) > 256) {
  		return -EBUSY;
  	}

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

  	mutex_init(&new->lock);

  	if (!tr->writesect)
  		new->readonly = 1;
  
  	gd = alloc_disk(1 << tr->part_bits);
  	if (!gd) {
  		list_del(&new->list);
  		return -ENOMEM;
  	}
  	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);

  
  	/* 2.5 has capacity in units of 512 bytes while still
  	   having BLOCK_SIZE_BITS set to 10. Just to keep us amused. */

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

  
  	gd->private_data = new;
  	new->blkcore_priv = gd;
  	gd->queue = tr->blkcore_priv->rq;
  
  	if (new->readonly)
  		set_disk_ro(gd, 1);
  
  	add_disk(gd);

  	return 0;
  }
  
  int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
  {

  	if (mutex_trylock(&mtd_table_mutex)) {

  		mutex_unlock(&mtd_table_mutex);

  		BUG();
  	}
  
  	list_del(&old->list);
  
  	del_gendisk(old->blkcore_priv);
  	put_disk(old->blkcore_priv);

  	return 0;
  }
  
  static void blktrans_notify_remove(struct mtd_info *mtd)
  {
  	struct list_head *this, *this2, *next;
  
  	list_for_each(this, &blktrans_majors) {
  		struct mtd_blktrans_ops *tr = list_entry(this, struct mtd_blktrans_ops, list);
  
  		list_for_each_safe(this2, next, &tr->devs) {
  			struct mtd_blktrans_dev *dev = list_entry(this2, struct mtd_blktrans_dev, list);
  
  			if (dev->mtd == mtd)
  				tr->remove_dev(dev);
  		}
  	}
  }
  
  static void blktrans_notify_add(struct mtd_info *mtd)
  {
  	struct list_head *this;
  
  	if (mtd->type == MTD_ABSENT)
  		return;
  
  	list_for_each(this, &blktrans_majors) {
  		struct mtd_blktrans_ops *tr = list_entry(this, struct mtd_blktrans_ops, 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)
  {
  	int ret, i;

  	/* 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);

  	tr->blkcore_priv = kzalloc(sizeof(*tr->blkcore_priv), GFP_KERNEL);

  	if (!tr->blkcore_priv)
  		return -ENOMEM;

  	mutex_lock(&mtd_table_mutex);

  
  	ret = register_blkdev(tr->major, tr->name);
  	if (ret) {
  		printk(KERN_WARNING "Unable to register %s block device on major %d: %d
  ",
  		       tr->name, tr->major, ret);
  		kfree(tr->blkcore_priv);

  		mutex_unlock(&mtd_table_mutex);

  		return ret;
  	}
  	spin_lock_init(&tr->blkcore_priv->queue_lock);

  
  	tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
  	if (!tr->blkcore_priv->rq) {
  		unregister_blkdev(tr->major, tr->name);
  		kfree(tr->blkcore_priv);

  		mutex_unlock(&mtd_table_mutex);

  		return -ENOMEM;
  	}
  
  	tr->blkcore_priv->rq->queuedata = tr;

  	blk_queue_hardsect_size(tr->blkcore_priv->rq, tr->blksize);
  	tr->blkshift = ffs(tr->blksize) - 1;

  	tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
  			"%sd", tr->name);
  	if (IS_ERR(tr->blkcore_priv->thread)) {

  		blk_cleanup_queue(tr->blkcore_priv->rq);
  		unregister_blkdev(tr->major, tr->name);
  		kfree(tr->blkcore_priv);

  		mutex_unlock(&mtd_table_mutex);

  		return PTR_ERR(tr->blkcore_priv->thread);

  	}

  	INIT_LIST_HEAD(&tr->devs);
  	list_add(&tr->list, &blktrans_majors);
  
  	for (i=0; i<MAX_MTD_DEVICES; i++) {
  		if (mtd_table[i] && mtd_table[i]->type != MTD_ABSENT)
  			tr->add_mtd(tr, mtd_table[i]);
  	}

  	mutex_unlock(&mtd_table_mutex);

  
  	return 0;
  }
  
  int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
  {
  	struct list_head *this, *next;

  	mutex_lock(&mtd_table_mutex);

  
  	/* Clean up the kernel thread */

  	kthread_stop(tr->blkcore_priv->thread);

  
  	/* Remove it from the list of active majors */
  	list_del(&tr->list);
  
  	list_for_each_safe(this, next, &tr->devs) {
  		struct mtd_blktrans_dev *dev = list_entry(this, struct mtd_blktrans_dev, list);
  		tr->remove_dev(dev);
  	}

  	blk_cleanup_queue(tr->blkcore_priv->rq);
  	unregister_blkdev(tr->major, tr->name);

  	mutex_unlock(&mtd_table_mutex);

  
  	kfree(tr->blkcore_priv);

  	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'");