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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Direct MTD block device access
4 *
5 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
6 * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
7 */
8
9#include <linux/fs.h>
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/sched.h>
14#include <linux/slab.h>
15#include <linux/types.h>
16#include <linux/vmalloc.h>
17
18#include <linux/mtd/mtd.h>
19#include <linux/mtd/blktrans.h>
20#include <linux/mutex.h>
21#include <linux/major.h>
22
23
24struct mtdblk_dev {
25 struct mtd_blktrans_dev mbd;
26 int count;
27 struct mutex cache_mutex;
28 unsigned char *cache_data;
29 unsigned long cache_offset;
30 unsigned int cache_size;
31 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
32};
33
34/*
35 * Cache stuff...
36 *
37 * Since typical flash erasable sectors are much larger than what Linux's
38 * buffer cache can handle, we must implement read-modify-write on flash
39 * sectors for each block write requests. To avoid over-erasing flash sectors
40 * and to speed things up, we locally cache a whole flash sector while it is
41 * being written to until a different sector is required.
42 */
43
44static int erase_write (struct mtd_info *mtd, unsigned long pos,
45 unsigned int len, const char *buf)
46{
47 struct erase_info erase;
48 size_t retlen;
49 int ret;
50
51 /*
52 * First, let's erase the flash block.
53 */
54 erase.addr = pos;
55 erase.len = len;
56
57 ret = mtd_erase(mtd, &erase);
58 if (ret) {
59 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
60 "on \"%s\" failed\n",
61 pos, len, mtd->name);
62 return ret;
63 }
64
65 /*
66 * Next, write the data to flash.
67 */
68
69 ret = mtd_write(mtd, pos, len, &retlen, buf);
70 if (ret)
71 return ret;
72 if (retlen != len)
73 return -EIO;
74 return 0;
75}
76
77
78static int write_cached_data (struct mtdblk_dev *mtdblk)
79{
80 struct mtd_info *mtd = mtdblk->mbd.mtd;
81 int ret;
82
83 if (mtdblk->cache_state != STATE_DIRTY)
84 return 0;
85
86 pr_debug("mtdblock: writing cached data for \"%s\" "
87 "at 0x%lx, size 0x%x\n", mtd->name,
88 mtdblk->cache_offset, mtdblk->cache_size);
89
90 ret = erase_write (mtd, mtdblk->cache_offset,
91 mtdblk->cache_size, mtdblk->cache_data);
92
93 /*
94 * Here we could arguably set the cache state to STATE_CLEAN.
95 * However this could lead to inconsistency since we will not
96 * be notified if this content is altered on the flash by other
97 * means. Let's declare it empty and leave buffering tasks to
98 * the buffer cache instead.
99 *
100 * If this cache_offset points to a bad block, data cannot be
101 * written to the device. Clear cache_state to avoid writing to
102 * bad blocks repeatedly.
103 */
104 if (ret == 0 || ret == -EIO)
105 mtdblk->cache_state = STATE_EMPTY;
106 return ret;
107}
108
109
110static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
111 int len, const char *buf)
112{
113 struct mtd_info *mtd = mtdblk->mbd.mtd;
114 unsigned int sect_size = mtdblk->cache_size;
115 size_t retlen;
116 int ret;
117
118 pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
119 mtd->name, pos, len);
120
121 if (!sect_size)
122 return mtd_write(mtd, pos, len, &retlen, buf);
123
124 while (len > 0) {
125 unsigned long sect_start = (pos/sect_size)*sect_size;
126 unsigned int offset = pos - sect_start;
127 unsigned int size = sect_size - offset;
128 if( size > len )
129 size = len;
130
131 if (size == sect_size) {
132 /*
133 * We are covering a whole sector. Thus there is no
134 * need to bother with the cache while it may still be
135 * useful for other partial writes.
136 */
137 ret = erase_write (mtd, pos, size, buf);
138 if (ret)
139 return ret;
140 } else {
141 /* Partial sector: need to use the cache */
142
143 if (mtdblk->cache_state == STATE_DIRTY &&
144 mtdblk->cache_offset != sect_start) {
145 ret = write_cached_data(mtdblk);
146 if (ret)
147 return ret;
148 }
149
150 if (mtdblk->cache_state == STATE_EMPTY ||
151 mtdblk->cache_offset != sect_start) {
152 /* fill the cache with the current sector */
153 mtdblk->cache_state = STATE_EMPTY;
154 ret = mtd_read(mtd, sect_start, sect_size,
155 &retlen, mtdblk->cache_data);
156 if (ret && !mtd_is_bitflip(ret))
157 return ret;
158 if (retlen != sect_size)
159 return -EIO;
160
161 mtdblk->cache_offset = sect_start;
162 mtdblk->cache_size = sect_size;
163 mtdblk->cache_state = STATE_CLEAN;
164 }
165
166 /* write data to our local cache */
167 memcpy (mtdblk->cache_data + offset, buf, size);
168 mtdblk->cache_state = STATE_DIRTY;
169 }
170
171 buf += size;
172 pos += size;
173 len -= size;
174 }
175
176 return 0;
177}
178
179
180static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
181 int len, char *buf)
182{
183 struct mtd_info *mtd = mtdblk->mbd.mtd;
184 unsigned int sect_size = mtdblk->cache_size;
185 size_t retlen;
186 int ret;
187
188 pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
189 mtd->name, pos, len);
190
191 if (!sect_size) {
192 ret = mtd_read(mtd, pos, len, &retlen, buf);
193 if (ret && !mtd_is_bitflip(ret))
194 return ret;
195 return 0;
196 }
197
198 while (len > 0) {
199 unsigned long sect_start = (pos/sect_size)*sect_size;
200 unsigned int offset = pos - sect_start;
201 unsigned int size = sect_size - offset;
202 if (size > len)
203 size = len;
204
205 /*
206 * Check if the requested data is already cached
207 * Read the requested amount of data from our internal cache if it
208 * contains what we want, otherwise we read the data directly
209 * from flash.
210 */
211 if (mtdblk->cache_state != STATE_EMPTY &&
212 mtdblk->cache_offset == sect_start) {
213 memcpy (buf, mtdblk->cache_data + offset, size);
214 } else {
215 ret = mtd_read(mtd, pos, size, &retlen, buf);
216 if (ret && !mtd_is_bitflip(ret))
217 return ret;
218 if (retlen != size)
219 return -EIO;
220 }
221
222 buf += size;
223 pos += size;
224 len -= size;
225 }
226
227 return 0;
228}
229
230static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
231 unsigned long block, char *buf)
232{
233 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
234 return do_cached_read(mtdblk, block<<9, 512, buf);
235}
236
237static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
238 unsigned long block, char *buf)
239{
240 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
241 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
242 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
243 if (!mtdblk->cache_data)
244 return -EINTR;
245 /* -EINTR is not really correct, but it is the best match
246 * documented in man 2 write for all cases. We could also
247 * return -EAGAIN sometimes, but why bother?
248 */
249 }
250 return do_cached_write(mtdblk, block<<9, 512, buf);
251}
252
253static int mtdblock_open(struct mtd_blktrans_dev *mbd)
254{
255 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
256
257 pr_debug("mtdblock_open\n");
258
259 if (mtdblk->count) {
260 mtdblk->count++;
261 return 0;
262 }
263
264 if (mtd_type_is_nand(mbd->mtd))
265 pr_warn_ratelimited("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n",
266 mbd->tr->name, mbd->mtd->name);
267
268 /* OK, it's not open. Create cache info for it */
269 mtdblk->count = 1;
270 mutex_init(&mtdblk->cache_mutex);
271 mtdblk->cache_state = STATE_EMPTY;
272 if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
273 mtdblk->cache_size = mbd->mtd->erasesize;
274 mtdblk->cache_data = NULL;
275 }
276
277 pr_debug("ok\n");
278
279 return 0;
280}
281
282static void mtdblock_release(struct mtd_blktrans_dev *mbd)
283{
284 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
285
286 pr_debug("mtdblock_release\n");
287
288 mutex_lock(&mtdblk->cache_mutex);
289 write_cached_data(mtdblk);
290 mutex_unlock(&mtdblk->cache_mutex);
291
292 if (!--mtdblk->count) {
293 /*
294 * It was the last usage. Free the cache, but only sync if
295 * opened for writing.
296 */
297 if (mbd->writable)
298 mtd_sync(mbd->mtd);
299 vfree(mtdblk->cache_data);
300 }
301
302 pr_debug("ok\n");
303}
304
305static int mtdblock_flush(struct mtd_blktrans_dev *dev)
306{
307 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
308 int ret;
309
310 mutex_lock(&mtdblk->cache_mutex);
311 ret = write_cached_data(mtdblk);
312 mutex_unlock(&mtdblk->cache_mutex);
313 mtd_sync(dev->mtd);
314 return ret;
315}
316
317static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
318{
319 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
320
321 if (!dev)
322 return;
323
324 dev->mbd.mtd = mtd;
325 dev->mbd.devnum = mtd->index;
326
327 dev->mbd.size = mtd->size >> 9;
328 dev->mbd.tr = tr;
329
330 if (!(mtd->flags & MTD_WRITEABLE))
331 dev->mbd.readonly = 1;
332
333 if (add_mtd_blktrans_dev(&dev->mbd))
334 kfree(dev);
335}
336
337static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
338{
339 del_mtd_blktrans_dev(dev);
340}
341
342static struct mtd_blktrans_ops mtdblock_tr = {
343 .name = "mtdblock",
344 .major = MTD_BLOCK_MAJOR,
345 .part_bits = 0,
346 .blksize = 512,
347 .open = mtdblock_open,
348 .flush = mtdblock_flush,
349 .release = mtdblock_release,
350 .readsect = mtdblock_readsect,
351 .writesect = mtdblock_writesect,
352 .add_mtd = mtdblock_add_mtd,
353 .remove_dev = mtdblock_remove_dev,
354 .owner = THIS_MODULE,
355};
356
357module_mtd_blktrans(mtdblock_tr);
358
359MODULE_LICENSE("GPL");
360MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
361MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Direct MTD block device access
4 *
5 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
6 * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
7 */
8
9#include <linux/fs.h>
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/sched.h>
14#include <linux/slab.h>
15#include <linux/types.h>
16#include <linux/vmalloc.h>
17
18#include <linux/mtd/mtd.h>
19#include <linux/mtd/blktrans.h>
20#include <linux/mutex.h>
21#include <linux/major.h>
22
23
24struct mtdblk_dev {
25 struct mtd_blktrans_dev mbd;
26 int count;
27 struct mutex cache_mutex;
28 unsigned char *cache_data;
29 unsigned long cache_offset;
30 unsigned int cache_size;
31 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
32};
33
34/*
35 * Cache stuff...
36 *
37 * Since typical flash erasable sectors are much larger than what Linux's
38 * buffer cache can handle, we must implement read-modify-write on flash
39 * sectors for each block write requests. To avoid over-erasing flash sectors
40 * and to speed things up, we locally cache a whole flash sector while it is
41 * being written to until a different sector is required.
42 */
43
44static int erase_write (struct mtd_info *mtd, unsigned long pos,
45 unsigned int len, const char *buf)
46{
47 struct erase_info erase;
48 size_t retlen;
49 int ret;
50
51 /*
52 * First, let's erase the flash block.
53 */
54 erase.addr = pos;
55 erase.len = len;
56
57 ret = mtd_erase(mtd, &erase);
58 if (ret) {
59 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
60 "on \"%s\" failed\n",
61 pos, len, mtd->name);
62 return ret;
63 }
64
65 /*
66 * Next, write the data to flash.
67 */
68
69 ret = mtd_write(mtd, pos, len, &retlen, buf);
70 if (ret)
71 return ret;
72 if (retlen != len)
73 return -EIO;
74 return 0;
75}
76
77
78static int write_cached_data (struct mtdblk_dev *mtdblk)
79{
80 struct mtd_info *mtd = mtdblk->mbd.mtd;
81 int ret;
82
83 if (mtdblk->cache_state != STATE_DIRTY)
84 return 0;
85
86 pr_debug("mtdblock: writing cached data for \"%s\" "
87 "at 0x%lx, size 0x%x\n", mtd->name,
88 mtdblk->cache_offset, mtdblk->cache_size);
89
90 ret = erase_write (mtd, mtdblk->cache_offset,
91 mtdblk->cache_size, mtdblk->cache_data);
92 if (ret)
93 return ret;
94
95 /*
96 * Here we could arguably set the cache state to STATE_CLEAN.
97 * However this could lead to inconsistency since we will not
98 * be notified if this content is altered on the flash by other
99 * means. Let's declare it empty and leave buffering tasks to
100 * the buffer cache instead.
101 */
102 mtdblk->cache_state = STATE_EMPTY;
103 return 0;
104}
105
106
107static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
108 int len, const char *buf)
109{
110 struct mtd_info *mtd = mtdblk->mbd.mtd;
111 unsigned int sect_size = mtdblk->cache_size;
112 size_t retlen;
113 int ret;
114
115 pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
116 mtd->name, pos, len);
117
118 if (!sect_size)
119 return mtd_write(mtd, pos, len, &retlen, buf);
120
121 while (len > 0) {
122 unsigned long sect_start = (pos/sect_size)*sect_size;
123 unsigned int offset = pos - sect_start;
124 unsigned int size = sect_size - offset;
125 if( size > len )
126 size = len;
127
128 if (size == sect_size) {
129 /*
130 * We are covering a whole sector. Thus there is no
131 * need to bother with the cache while it may still be
132 * useful for other partial writes.
133 */
134 ret = erase_write (mtd, pos, size, buf);
135 if (ret)
136 return ret;
137 } else {
138 /* Partial sector: need to use the cache */
139
140 if (mtdblk->cache_state == STATE_DIRTY &&
141 mtdblk->cache_offset != sect_start) {
142 ret = write_cached_data(mtdblk);
143 if (ret)
144 return ret;
145 }
146
147 if (mtdblk->cache_state == STATE_EMPTY ||
148 mtdblk->cache_offset != sect_start) {
149 /* fill the cache with the current sector */
150 mtdblk->cache_state = STATE_EMPTY;
151 ret = mtd_read(mtd, sect_start, sect_size,
152 &retlen, mtdblk->cache_data);
153 if (ret)
154 return ret;
155 if (retlen != sect_size)
156 return -EIO;
157
158 mtdblk->cache_offset = sect_start;
159 mtdblk->cache_size = sect_size;
160 mtdblk->cache_state = STATE_CLEAN;
161 }
162
163 /* write data to our local cache */
164 memcpy (mtdblk->cache_data + offset, buf, size);
165 mtdblk->cache_state = STATE_DIRTY;
166 }
167
168 buf += size;
169 pos += size;
170 len -= size;
171 }
172
173 return 0;
174}
175
176
177static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
178 int len, char *buf)
179{
180 struct mtd_info *mtd = mtdblk->mbd.mtd;
181 unsigned int sect_size = mtdblk->cache_size;
182 size_t retlen;
183 int ret;
184
185 pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
186 mtd->name, pos, len);
187
188 if (!sect_size)
189 return mtd_read(mtd, pos, len, &retlen, buf);
190
191 while (len > 0) {
192 unsigned long sect_start = (pos/sect_size)*sect_size;
193 unsigned int offset = pos - sect_start;
194 unsigned int size = sect_size - offset;
195 if (size > len)
196 size = len;
197
198 /*
199 * Check if the requested data is already cached
200 * Read the requested amount of data from our internal cache if it
201 * contains what we want, otherwise we read the data directly
202 * from flash.
203 */
204 if (mtdblk->cache_state != STATE_EMPTY &&
205 mtdblk->cache_offset == sect_start) {
206 memcpy (buf, mtdblk->cache_data + offset, size);
207 } else {
208 ret = mtd_read(mtd, pos, size, &retlen, buf);
209 if (ret)
210 return ret;
211 if (retlen != size)
212 return -EIO;
213 }
214
215 buf += size;
216 pos += size;
217 len -= size;
218 }
219
220 return 0;
221}
222
223static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
224 unsigned long block, char *buf)
225{
226 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
227 return do_cached_read(mtdblk, block<<9, 512, buf);
228}
229
230static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
231 unsigned long block, char *buf)
232{
233 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
234 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
235 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
236 if (!mtdblk->cache_data)
237 return -EINTR;
238 /* -EINTR is not really correct, but it is the best match
239 * documented in man 2 write for all cases. We could also
240 * return -EAGAIN sometimes, but why bother?
241 */
242 }
243 return do_cached_write(mtdblk, block<<9, 512, buf);
244}
245
246static int mtdblock_open(struct mtd_blktrans_dev *mbd)
247{
248 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
249
250 pr_debug("mtdblock_open\n");
251
252 if (mtdblk->count) {
253 mtdblk->count++;
254 return 0;
255 }
256
257 /* OK, it's not open. Create cache info for it */
258 mtdblk->count = 1;
259 mutex_init(&mtdblk->cache_mutex);
260 mtdblk->cache_state = STATE_EMPTY;
261 if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
262 mtdblk->cache_size = mbd->mtd->erasesize;
263 mtdblk->cache_data = NULL;
264 }
265
266 pr_debug("ok\n");
267
268 return 0;
269}
270
271static void mtdblock_release(struct mtd_blktrans_dev *mbd)
272{
273 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
274
275 pr_debug("mtdblock_release\n");
276
277 mutex_lock(&mtdblk->cache_mutex);
278 write_cached_data(mtdblk);
279 mutex_unlock(&mtdblk->cache_mutex);
280
281 if (!--mtdblk->count) {
282 /*
283 * It was the last usage. Free the cache, but only sync if
284 * opened for writing.
285 */
286 if (mbd->file_mode & FMODE_WRITE)
287 mtd_sync(mbd->mtd);
288 vfree(mtdblk->cache_data);
289 }
290
291 pr_debug("ok\n");
292}
293
294static int mtdblock_flush(struct mtd_blktrans_dev *dev)
295{
296 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
297
298 mutex_lock(&mtdblk->cache_mutex);
299 write_cached_data(mtdblk);
300 mutex_unlock(&mtdblk->cache_mutex);
301 mtd_sync(dev->mtd);
302 return 0;
303}
304
305static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
306{
307 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
308
309 if (!dev)
310 return;
311
312 dev->mbd.mtd = mtd;
313 dev->mbd.devnum = mtd->index;
314
315 dev->mbd.size = mtd->size >> 9;
316 dev->mbd.tr = tr;
317
318 if (!(mtd->flags & MTD_WRITEABLE))
319 dev->mbd.readonly = 1;
320
321 if (add_mtd_blktrans_dev(&dev->mbd))
322 kfree(dev);
323}
324
325static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
326{
327 del_mtd_blktrans_dev(dev);
328}
329
330static struct mtd_blktrans_ops mtdblock_tr = {
331 .name = "mtdblock",
332 .major = MTD_BLOCK_MAJOR,
333 .part_bits = 0,
334 .blksize = 512,
335 .open = mtdblock_open,
336 .flush = mtdblock_flush,
337 .release = mtdblock_release,
338 .readsect = mtdblock_readsect,
339 .writesect = mtdblock_writesect,
340 .add_mtd = mtdblock_add_mtd,
341 .remove_dev = mtdblock_remove_dev,
342 .owner = THIS_MODULE,
343};
344
345static int __init init_mtdblock(void)
346{
347 return register_mtd_blktrans(&mtdblock_tr);
348}
349
350static void __exit cleanup_mtdblock(void)
351{
352 deregister_mtd_blktrans(&mtdblock_tr);
353}
354
355module_init(init_mtdblock);
356module_exit(cleanup_mtdblock);
357
358
359MODULE_LICENSE("GPL");
360MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
361MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");