1 files changed, 369 insertions, 0 deletions

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
new file mode 100644
index 000000000..9e5bbb545
--- /dev/null
+++ b/drivers/mtd/mtdblock.c
@@ -0,0 +1,369 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Direct MTD block device access
+ *
+ * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
+ * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
+ */
+
+#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,
+			unsigned 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);
+
+	/*
+	 * 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.
+	 *
+	 * If this cache_offset points to a bad block, data cannot be
+	 * written to the device. Clear cache_state to avoid writing to
+	 * bad blocks repeatedly.
+	 */
+	if (ret == 0 || ret == -EIO)
+		mtdblk->cache_state = STATE_EMPTY;
+	return ret;
+}
+
+
+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 && !mtd_is_bitflip(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) {
+		ret = mtd_read(mtd, pos, len, &retlen, buf);
+		if (ret && !mtd_is_bitflip(ret))
+			return ret;
+		return 0;
+	}
+
+	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 && !mtd_is_bitflip(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);
+	int ret;
+
+	mutex_lock(&mtdblk->cache_mutex);
+	ret = write_cached_data(mtdblk);
+	mutex_unlock(&mtdblk->cache_mutex);
+	mtd_sync(dev->mtd);
+	return ret;
+}
+
+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");