mtdblock.c

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/* 
 * Direct MTD block device access
 *
 * $Id: mtdblock.c,v 1.38 2000/11/27 08:50:22 dwmw2 Exp $
 *
 * 02-nov-2000	Nicolas Pitre		Added read-modify-write with cache
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/malloc.h>
#include <linux/mtd/mtd.h>

#define MAJOR_NR MTD_BLOCK_MAJOR
#define DEVICE_NAME "mtdblock"
#define DEVICE_REQUEST mtdblock_request
#define DEVICE_NR(device) (device)
#define DEVICE_ON(device)
#define DEVICE_OFF(device)
#define DEVICE_NO_RANDOM
#include <linux/blk.h>
/* for old kernels... */
#ifndef QUEUE_EMPTY
#define QUEUE_EMPTY  (!CURRENT)
#endif
#if LINUX_VERSION_CODE < 0x20300
#define QUEUE_PLUGGED (blk_dev[MAJOR_NR].plug_tq.sync)
#else
#define QUEUE_PLUGGED (blk_dev[MAJOR_NR].request_queue.plugged)
#endif

#ifdef CONFIG_DEVFS_FS
#include <linux/devfs_fs_kernel.h>
static void mtd_notify_add(struct mtd_info* mtd);
static void mtd_notify_remove(struct mtd_info* mtd);
static struct mtd_notifier notifier = {
        mtd_notify_add,
        mtd_notify_remove,
        NULL
};
static devfs_handle_t devfs_dir_handle = NULL;
static devfs_handle_t devfs_rw_handle[MAX_MTD_DEVICES];
#endif

static struct mtdblk_dev {
	struct mtd_info *mtd; /* Locked */
	int count;
	struct semaphore cache_sem;
	unsigned char *cache_data;
	unsigned long cache_offset;
	unsigned int cache_size;
	enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
} *mtdblks[MAX_MTD_DEVICES];

static spinlock_t mtdblks_lock;

static int mtd_sizes[MAX_MTD_DEVICES];
static int mtd_blksizes[MAX_MTD_DEVICES];


/*
 * Cache stuff...
 * 
 * Since typical flash erasable sectors are much larger than what Linux's
 * buffer cache can handle, we must implement read-modify-write on flash
 * sectors for each block write requests.  To avoid over-erasing flash sectors
 * and to speed things up, we locally cache a whole flash sector while it is
 * being written to until a different sector is required.
 */

static void erase_callback(struct erase_info *done)
{
	wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
	wake_up(wait_q);
}

static int erase_write (struct mtd_info *mtd, unsigned long pos, 
			int len, const char *buf)
{
	struct erase_info erase;
	DECLARE_WAITQUEUE(wait, current);
	wait_queue_head_t wait_q;
	size_t retlen;
	int ret;

	/*
	 * First, let's erase the flash block.
	 */

	init_waitqueue_head(&wait_q);
	erase.mtd = mtd;
	erase.callback = erase_callback;
	erase.addr = pos;
	erase.len = len;
	erase.priv = (u_long)&wait_q;

	set_current_state(TASK_INTERRUPTIBLE);
	add_wait_queue(&wait_q, &wait);

	ret = MTD_ERASE(mtd, &erase);
	if (ret) {
		set_current_state(TASK_RUNNING);
		remove_wait_queue(&wait_q, &wait);
		printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
				     "on \"%s\" failed\n",
			pos, len, mtd->name);
		return ret;
	}

	schedule();  /* Wait for erase to finish. */
	remove_wait_queue(&wait_q, &wait);

	/*
	 * Next, writhe data to flash.
	 */

	ret = MTD_WRITE (mtd, pos, len, &retlen, buf);
	if (ret)
		return ret;
	if (retlen != len)
		return -EIO;
	return 0;
}


static int write_cached_data (struct mtdblk_dev *mtdblk)
{
	struct mtd_info *mtd = mtdblk->mtd;
	int ret;

	if (mtdblk->cache_state != STATE_DIRTY)
		return 0;

	DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
			"at 0x%lx, size 0x%x\n", mtd->name, 
			mtdblk->cache_offset, mtdblk->cache_size);
	
	ret = erase_write (mtd, mtdblk->cache_offset, 
			   mtdblk->cache_size, mtdblk->cache_data);
	if (ret)
		return ret;

	/*
	 * Here we could argably set the cache state to STATE_CLEAN.
	 * However this could lead to inconsistency since we will not 
	 * be notified if this content is altered on the flash by other 
	 * means.  Let's declare it empty and leave buffering tasks to
	 * the buffer cache instead.
	 */
	mtdblk->cache_state = STATE_EMPTY;
	return 0;
}


static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 
			    int len, const char *buf)
{
	struct mtd_info *mtd = mtdblk->mtd;
	unsigned int sect_size = mtd->erasesize;
	size_t retlen;
	int ret;

	DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
		mtd->name, pos, len);
	
	while (len > 0) {
		unsigned long sect_start = (pos/sect_size)*sect_size;
		unsigned int offset = pos - sect_start;
		unsigned int size = sect_size - offset;
		if( size > len ) 
			size = len;

		if (size == sect_size) {
			/* 
			 * We are covering a whole sector.  Thus there is no
			 * need to bother with the cache while it may still be
			 * useful for other partial writes.
			 */
			ret = erase_write (mtd, pos, size, buf);
			if (ret)
				return ret;
		} else {
			/* Partial sector: need to use the cache */

			if (mtdblk->cache_state == STATE_DIRTY &&
			    mtdblk->cache_offset != sect_start) {
				ret = write_cached_data(mtdblk);
				if (ret) 
					return ret;
			}

			if (mtdblk->cache_state == STATE_EMPTY ||
			    mtdblk->cache_offset != sect_start) {
				/* fill the cache with the current sector */
				mtdblk->cache_state = STATE_EMPTY;
				ret = MTD_READ(mtd, sect_start, sect_size, &retlen, mtdblk->cache_data);
				if (ret)
					return ret;
				if (retlen != sect_size)
					return -EIO;

				mtdblk->cache_offset = sect_start;
				mtdblk->cache_size = sect_size;
				mtdblk->cache_state = STATE_CLEAN;
			}

			/* write data to our local cache */
			memcpy (mtdblk->cache_data + offset, buf, size);
			mtdblk->cache_state = STATE_DIRTY;
		}

		buf += size;
		pos += size;
		len -= size;
	}

	return 0;
}


static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 
			   int len, char *buf)
{
	struct mtd_info *mtd = mtdblk->mtd;
	unsigned int sect_size = mtd->erasesize;
	size_t retlen;
	int ret;

	DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 
			mtd->name, pos, len);
	
	while (len > 0) {
		unsigned long sect_start = (pos/sect_size)*sect_size;
		unsigned int offset = pos - sect_start;
		unsigned int size = sect_size - offset;
		if (size > len) 
			size = len;

		/*
		 * Check if the requested data is already cached
		 * Read the requested amount of data from our internal cache if it
		 * contains what we want, otherwise we read the data directly
		 * from flash.
		 */
		if (mtdblk->cache_state != STATE_EMPTY &&
		    mtdblk->cache_offset == sect_start) {
			memcpy (buf, mtdblk->cache_data + offset, size);
		} else {
			ret = MTD_READ (mtd, pos, size, &retlen, buf);
			if (ret)
				return ret;
			if (retlen != size)
				return -EIO;
		}

		buf += size;
		pos += size;
		len -= size;
	}

	return 0;
}



static int mtdblock_open(struct inode *inode, struct file *file)
{
	struct mtdblk_dev *mtdblk;
	int dev;

	DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
	
	if (!inode)
		return -EINVAL;
	
	dev = MINOR(inode->i_rdev);
	if (dev >= MAX_MTD_DEVICES)
		return -EINVAL;
	
	MOD_INC_USE_COUNT;

	spin_lock(&mtdblks_lock);

	/* If it's already open, no need to piss about. */
	if (mtdblks[dev]) {
		mtdblks[dev]->count++;
		spin_unlock(&mtdblks_lock);
		return 0;
	}
	
	/* OK, it's not open. Try to find it */

	/* First we have to drop the lock, because we have to
	   to things which might sleep.
	*/
	spin_unlock(&mtdblks_lock);

	mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
	if (!mtdblk) {
		MOD_DEC_USE_COUNT;
		return -ENOMEM;
	}
	memset(mtdblk, 0, sizeof(*mtdblk));
	mtdblk->count = 1;
	mtdblk->mtd = get_mtd_device(NULL, dev);

	if (!mtdblk->mtd) {
		kfree(mtdblk);
		MOD_DEC_USE_COUNT;
		return -ENODEV;
	}

	init_MUTEX (&mtdblk->cache_sem);
	mtdblk->cache_state = STATE_EMPTY;
	mtdblk->cache_size = mtdblk->mtd->erasesize;
	mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize);
	if (!mtdblk->cache_data) {
		put_mtd_device(mtdblk->mtd);
		kfree(mtdblk);
		MOD_DEC_USE_COUNT;
		return -ENOMEM;
	}

	/* OK, we've created a new one. Add it to the list. */

	spin_lock(&mtdblks_lock);

	if (mtdblks[dev]) {
		/* Another CPU made one at the same time as us. */
		mtdblks[dev]->count++;
		spin_unlock(&mtdblks_lock);
		put_mtd_device(mtdblk->mtd);
		vfree(mtdblk->cache_data);
		kfree(mtdblk);
		return 0;
	}