// 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_ratelimited("%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->writable)			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_obj(*dev); 	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");