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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 <[email protected]>
6 * Copyright © 2000-2003 Nicolas Pitre <[email protected]>
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_obj(*dev);
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 <[email protected]> et al.");
361MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");