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357 lines
8.6 KiB
357 lines
8.6 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Direct MTD block device access |
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* |
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* Copyright © 1999-2010 David Woodhouse <[email protected]> |
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* Copyright © 2000-2003 Nicolas Pitre <[email protected]> |
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*/ |
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#include <linux/fs.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/types.h> |
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#include <linux/vmalloc.h> |
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#include <linux/mtd/mtd.h> |
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#include <linux/mtd/blktrans.h> |
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#include <linux/mutex.h> |
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#include <linux/major.h> |
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struct mtdblk_dev { |
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struct mtd_blktrans_dev mbd; |
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int count; |
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struct mutex cache_mutex; |
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unsigned char *cache_data; |
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unsigned long cache_offset; |
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unsigned int cache_size; |
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enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state; |
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}; |
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/* |
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* Cache stuff... |
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* |
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* Since typical flash erasable sectors are much larger than what Linux's |
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* buffer cache can handle, we must implement read-modify-write on flash |
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* sectors for each block write requests. To avoid over-erasing flash sectors |
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* and to speed things up, we locally cache a whole flash sector while it is |
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* being written to until a different sector is required. |
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*/ |
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static int erase_write (struct mtd_info *mtd, unsigned long pos, |
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unsigned int len, const char *buf) |
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{ |
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struct erase_info erase; |
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size_t retlen; |
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int ret; |
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/* |
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* First, let's erase the flash block. |
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*/ |
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erase.addr = pos; |
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erase.len = len; |
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ret = mtd_erase(mtd, &erase); |
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if (ret) { |
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printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " |
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"on \"%s\" failed\n", |
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pos, len, mtd->name); |
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return ret; |
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} |
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/* |
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* Next, write the data to flash. |
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*/ |
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ret = mtd_write(mtd, pos, len, &retlen, buf); |
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if (ret) |
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return ret; |
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if (retlen != len) |
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return -EIO; |
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return 0; |
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} |
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static int write_cached_data (struct mtdblk_dev *mtdblk) |
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{ |
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struct mtd_info *mtd = mtdblk->mbd.mtd; |
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int ret; |
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if (mtdblk->cache_state != STATE_DIRTY) |
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return 0; |
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pr_debug("mtdblock: writing cached data for \"%s\" " |
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"at 0x%lx, size 0x%x\n", mtd->name, |
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mtdblk->cache_offset, mtdblk->cache_size); |
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ret = erase_write (mtd, mtdblk->cache_offset, |
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mtdblk->cache_size, mtdblk->cache_data); |
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/* |
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* Here we could arguably set the cache state to STATE_CLEAN. |
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* However this could lead to inconsistency since we will not |
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* be notified if this content is altered on the flash by other |
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* means. Let's declare it empty and leave buffering tasks to |
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* the buffer cache instead. |
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* |
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* If this cache_offset points to a bad block, data cannot be |
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* written to the device. Clear cache_state to avoid writing to |
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* bad blocks repeatedly. |
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*/ |
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if (ret == 0 || ret == -EIO) |
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mtdblk->cache_state = STATE_EMPTY; |
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return ret; |
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} |
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static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, |
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int len, const char *buf) |
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{ |
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struct mtd_info *mtd = mtdblk->mbd.mtd; |
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unsigned int sect_size = mtdblk->cache_size; |
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size_t retlen; |
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int ret; |
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pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", |
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mtd->name, pos, len); |
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if (!sect_size) |
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return mtd_write(mtd, pos, len, &retlen, buf); |
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while (len > 0) { |
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unsigned long sect_start = (pos/sect_size)*sect_size; |
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unsigned int offset = pos - sect_start; |
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unsigned int size = sect_size - offset; |
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if( size > len ) |
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size = len; |
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if (size == sect_size) { |
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/* |
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* We are covering a whole sector. Thus there is no |
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* need to bother with the cache while it may still be |
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* useful for other partial writes. |
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*/ |
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ret = erase_write (mtd, pos, size, buf); |
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if (ret) |
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return ret; |
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} else { |
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/* Partial sector: need to use the cache */ |
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if (mtdblk->cache_state == STATE_DIRTY && |
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mtdblk->cache_offset != sect_start) { |
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ret = write_cached_data(mtdblk); |
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if (ret) |
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return ret; |
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} |
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if (mtdblk->cache_state == STATE_EMPTY || |
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mtdblk->cache_offset != sect_start) { |
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/* fill the cache with the current sector */ |
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mtdblk->cache_state = STATE_EMPTY; |
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ret = mtd_read(mtd, sect_start, sect_size, |
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&retlen, mtdblk->cache_data); |
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if (ret) |
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return ret; |
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if (retlen != sect_size) |
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return -EIO; |
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mtdblk->cache_offset = sect_start; |
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mtdblk->cache_size = sect_size; |
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mtdblk->cache_state = STATE_CLEAN; |
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} |
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/* write data to our local cache */ |
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memcpy (mtdblk->cache_data + offset, buf, size); |
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mtdblk->cache_state = STATE_DIRTY; |
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} |
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buf += size; |
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pos += size; |
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len -= size; |
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} |
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return 0; |
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} |
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static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, |
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int len, char *buf) |
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{ |
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struct mtd_info *mtd = mtdblk->mbd.mtd; |
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unsigned int sect_size = mtdblk->cache_size; |
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size_t retlen; |
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int ret; |
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pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", |
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mtd->name, pos, len); |
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if (!sect_size) |
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return mtd_read(mtd, pos, len, &retlen, buf); |
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while (len > 0) { |
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unsigned long sect_start = (pos/sect_size)*sect_size; |
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unsigned int offset = pos - sect_start; |
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unsigned int size = sect_size - offset; |
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if (size > len) |
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size = len; |
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/* |
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* Check if the requested data is already cached |
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* Read the requested amount of data from our internal cache if it |
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* contains what we want, otherwise we read the data directly |
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* from flash. |
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*/ |
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if (mtdblk->cache_state != STATE_EMPTY && |
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mtdblk->cache_offset == sect_start) { |
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memcpy (buf, mtdblk->cache_data + offset, size); |
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} else { |
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ret = mtd_read(mtd, pos, size, &retlen, buf); |
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if (ret) |
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return ret; |
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if (retlen != size) |
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return -EIO; |
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} |
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buf += size; |
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pos += size; |
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len -= size; |
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} |
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return 0; |
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} |
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static int mtdblock_readsect(struct mtd_blktrans_dev *dev, |
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unsigned long block, char *buf) |
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{ |
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struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); |
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return do_cached_read(mtdblk, block<<9, 512, buf); |
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} |
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static int mtdblock_writesect(struct mtd_blktrans_dev *dev, |
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unsigned long block, char *buf) |
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{ |
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struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); |
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if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { |
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mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize); |
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if (!mtdblk->cache_data) |
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return -EINTR; |
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/* -EINTR is not really correct, but it is the best match |
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* documented in man 2 write for all cases. We could also |
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* return -EAGAIN sometimes, but why bother? |
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*/ |
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} |
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return do_cached_write(mtdblk, block<<9, 512, buf); |
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} |
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static int mtdblock_open(struct mtd_blktrans_dev *mbd) |
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{ |
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struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); |
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pr_debug("mtdblock_open\n"); |
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if (mtdblk->count) { |
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mtdblk->count++; |
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return 0; |
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} |
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/* OK, it's not open. Create cache info for it */ |
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mtdblk->count = 1; |
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mutex_init(&mtdblk->cache_mutex); |
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mtdblk->cache_state = STATE_EMPTY; |
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if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) { |
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mtdblk->cache_size = mbd->mtd->erasesize; |
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mtdblk->cache_data = NULL; |
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} |
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pr_debug("ok\n"); |
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return 0; |
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} |
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static void mtdblock_release(struct mtd_blktrans_dev *mbd) |
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{ |
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struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); |
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pr_debug("mtdblock_release\n"); |
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mutex_lock(&mtdblk->cache_mutex); |
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write_cached_data(mtdblk); |
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mutex_unlock(&mtdblk->cache_mutex); |
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if (!--mtdblk->count) { |
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/* |
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* It was the last usage. Free the cache, but only sync if |
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* opened for writing. |
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*/ |
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if (mbd->file_mode & FMODE_WRITE) |
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mtd_sync(mbd->mtd); |
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vfree(mtdblk->cache_data); |
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} |
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pr_debug("ok\n"); |
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} |
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static int mtdblock_flush(struct mtd_blktrans_dev *dev) |
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{ |
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struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); |
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int ret; |
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mutex_lock(&mtdblk->cache_mutex); |
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ret = write_cached_data(mtdblk); |
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mutex_unlock(&mtdblk->cache_mutex); |
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mtd_sync(dev->mtd); |
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return ret; |
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} |
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static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) |
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{ |
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struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); |
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if (!dev) |
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return; |
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dev->mbd.mtd = mtd; |
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dev->mbd.devnum = mtd->index; |
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dev->mbd.size = mtd->size >> 9; |
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dev->mbd.tr = tr; |
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if (!(mtd->flags & MTD_WRITEABLE)) |
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dev->mbd.readonly = 1; |
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if (mtd_type_is_nand(mtd)) |
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pr_warn("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n", |
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tr->name, mtd->name); |
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if (add_mtd_blktrans_dev(&dev->mbd)) |
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kfree(dev); |
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} |
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static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) |
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{ |
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del_mtd_blktrans_dev(dev); |
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} |
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static struct mtd_blktrans_ops mtdblock_tr = { |
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.name = "mtdblock", |
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.major = MTD_BLOCK_MAJOR, |
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.part_bits = 0, |
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.blksize = 512, |
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.open = mtdblock_open, |
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.flush = mtdblock_flush, |
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.release = mtdblock_release, |
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.readsect = mtdblock_readsect, |
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.writesect = mtdblock_writesect, |
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.add_mtd = mtdblock_add_mtd, |
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.remove_dev = mtdblock_remove_dev, |
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.owner = THIS_MODULE, |
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}; |
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module_mtd_blktrans(mtdblock_tr); |
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MODULE_LICENSE("GPL"); |
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MODULE_AUTHOR("Nicolas Pitre <[email protected]> et al."); |
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MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
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