/*
* Direct MTD block device access
*
* Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
* Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
*
* 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/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/blktrans.h>
#include <linux/mutex.h>
struct mtdblk_dev {
struct mtd_blktrans_dev mbd;
int count;
struct mutex cache_mutex;
unsigned char *cache_data;
unsigned long cache_offset;
unsigned int cache_size;
enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
};
static DEFINE_MUTEX(mtdblks_lock);
/*
* 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, write the 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->mbd.mtd;
int ret;
if (mtdblk->cache_state != STATE_DIRTY)
return 0;
pr_debug("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 arguably 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->mbd.mtd;
unsigned int sect_size = mtdblk->cache_size;
size_t retlen;
int ret;
pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
mtd->name, pos, len);
if (!sect_size)
return mtd->write(mtd, pos, len, &retlen, buf);
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->mbd.mtd;
unsigned int sect_size = mtdblk->cache_size;
size_t retlen;
int ret;
pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
mtd->name, pos, len);
if (!sect_size)
return mtd->read(mtd, pos, len, &retlen, buf);
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_readsect(struct mtd_blktrans_dev *dev,
unsigned long block, char *buf)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
return do_cached_read(mtdblk, block<<9, 512, buf);
}
static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
unsigned long block, char *buf)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
if (!mtdblk->cache_data)
return -EINTR;
/* -EINTR is not really correct, but it is the best match
* documented in man 2 write for all cases. We could also
* return -EAGAIN sometimes, but why bother?
*/
}
return do_cached_write(mtdblk, block<<9, 512, buf);
}
static int mtdblock_open(struct mtd_blktrans_dev *mbd)
{
struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
pr_debug("mtdblock_open\n");
mutex_lock(&mtdblks_lock);
if (mtdblk->count) {
mtdblk->count++;
mutex_unlock(&mtdblks_lock);
return 0;
}
/* OK, it's not open. Create cache info for it */
mtdblk->count = 1;
mutex_init(&mtdblk->cache_mutex);
mtdblk->cache_state = STATE_EMPTY;
if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
mtdblk->cache_size = mbd->mtd->erasesize;
mtdblk->cache_data = NULL;
}
mutex_unlock(&mtdblks_lock);
pr_debug("ok\n");
return 0;
}
static int mtdblock_release(struct mtd_blktrans_dev *mbd)
{
struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
pr_debug("mtdblock_release\n");
mutex_lock(&mtdblks_lock);
mutex_lock(&mtdblk->cache_mutex);
write_cached_data(mtdblk);
mutex_unlock(&mtdblk->cache_mutex);
if (!--mtdblk->count) {
/* It was the last usage. Free the cache */
if (mbd->mtd->sync)
mbd->mtd->sync(mbd->mtd);
vfree(mtdblk->cache_data);
}
mutex_unlock(&mtdblks_lock);
pr_debug("ok\n");
return 0;
}
static int mtdblock_flush(struct mtd_blktrans_dev *dev)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
mutex_lock(&mtdblk->cache_mutex);
write_cached_data(mtdblk);
mutex_unlock(&mtdblk->cache_mutex);
if (dev->mtd->sync)
dev->mtd->sync(dev->mtd);
return 0;
}
static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (!dev)
return;
dev->mbd.mtd = mtd;
dev->mbd.devnum = mtd->index;
dev->mbd.size = mtd->size >> 9;
dev->mbd.tr = tr;
if (!(mtd->flags & MTD_WRITEABLE))
dev->mbd.readonly = 1;
if (add_mtd_blktrans_dev(&dev->mbd))
kfree(dev);
}
static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
{
del_mtd_blktrans_dev(dev);
}
static struct mtd_blktrans_ops mtdblock_tr = {
.name = "mtdblock",
.major = 31,
.part_bits = 0,
.blksize = 512,
.open = mtdblock_open,
.flush = mtdblock_flush,
.release = mtdblock_release,
.readsect = mtdblock_readsect,
.writesect = mtdblock_writesect,
.add_mtd = mtdblock_add_mtd,
.remove_dev = mtdblock_remove_dev,
.owner = THIS_MODULE,
};
static int __init init_mtdblock(void)
{
return register_mtd_blktrans(&mtdblock_tr);
}
static void __exit cleanup_mtdblock(void)
{
deregister_mtd_blktrans(&mtdblock_tr);
}
module_init(init_mtdblock);
module_exit(cleanup_mtdblock);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
