diff options
Diffstat (limited to 'drivers/mtd/mtdblock.c')
| -rw-r--r-- | drivers/mtd/mtdblock.c | 375 |
1 files changed, 375 insertions, 0 deletions
diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c new file mode 100644 index 000000000..a5b1933c0 --- /dev/null +++ b/drivers/mtd/mtdblock.c @@ -0,0 +1,375 @@ +/* + * 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> +#include <linux/major.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; +}; + +/* + * 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 int erase_write (struct mtd_info *mtd, unsigned long pos, + int len, const char *buf) +{ + struct erase_info erase; + size_t retlen; + int ret; + + /* + * First, let's erase the flash block. + */ + erase.addr = pos; + erase.len = len; + + ret = mtd_erase(mtd, &erase); + if (ret) { + printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " + "on \"%s\" failed\n", + pos, len, mtd->name); + return ret; + } + + /* + * 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"); + + if (mtdblk->count) { + mtdblk->count++; + 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; + } + + pr_debug("ok\n"); + + return 0; +} + +static void 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(&mtdblk->cache_mutex); + write_cached_data(mtdblk); + mutex_unlock(&mtdblk->cache_mutex); + + if (!--mtdblk->count) { + /* + * It was the last usage. Free the cache, but only sync if + * opened for writing. + */ + if (mbd->file_mode & FMODE_WRITE) + mtd_sync(mbd->mtd); + vfree(mtdblk->cache_data); + } + + pr_debug("ok\n"); +} + +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); + 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 = MTD_BLOCK_MAJOR, + .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"); |