/* * Direct MTD block device access * * Copyright © 1999-2010 David Woodhouse * Copyright © 2000-2003 Nicolas Pitre * * 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 #include #include #include #include #include #include #include #include #include #include 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 struct 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; 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 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; DEBUG(MTD_DEBUG_LEVEL2, "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; DEBUG(MTD_DEBUG_LEVEL2, "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); DEBUG(MTD_DEBUG_LEVEL1,"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); DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); return 0; } static int mtdblock_release(struct mtd_blktrans_dev *mbd) { struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); DEBUG(MTD_DEBUG_LEVEL1, "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); DEBUG(MTD_DEBUG_LEVEL1, "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) { mutex_init(&mtdblks_lock); 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 et al."); MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");