--- /dev/null
+/*
+ * 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 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");
+
+ 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");
Code Review / kvmfornfv.git / blobdiff