drivers/mtd/mtdblock.c - linux - Git at Google

 // 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;
 	}

 	if (mtd_type_is_nand(mbd->mtd))
 		pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
 			mbd->tr->name, mbd->mtd->name);

 	/* 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,
 };

 module_mtd_blktrans(mtdblock_tr);

 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");
	// 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;
	}

	if (mtd_type_is_nand(mbd->mtd))
	pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
	mbd->tr->name, mbd->mtd->name);

	/* 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,
	};

	module_mtd_blktrans(mtdblock_tr);

	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");