1 /*
2 * Direct MTD block device access
3 *
4 * (C) 2000-2003 Nicolas Pitre <nico@cam.org>
5 * (C) 1999-2003 David Woodhouse <dwmw2@infradead.org>
6 */
7
8 #include <linux/fs.h>
9 #include <linux/init.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/sched.h>
13 #include <linux/slab.h>
14 #include <linux/types.h>
15 #include <linux/vmalloc.h>
16
17 #include <linux/mtd/mtd.h>
18 #include <linux/mtd/blktrans.h>
19 #include <linux/mutex.h>
20
21
22 static struct mtdblk_dev {
23 struct mtd_info *mtd;
24 int count;
25 struct mutex cache_mutex;
26 unsigned char *cache_data;
27 unsigned long cache_offset;
28 unsigned int cache_size;
29 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
30 } *mtdblks[MAX_MTD_DEVICES];
31
32 static struct mutex mtdblks_lock;
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
44 static void erase_callback(struct erase_info *done)
45 {
46 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
47 wake_up(wait_q);
48 }
49
50 static int erase_write (struct mtd_info *mtd, unsigned long pos,
51 int len, const char *buf)
52 {
53 struct erase_info erase;
54 DECLARE_WAITQUEUE(wait, current);
55 wait_queue_head_t wait_q;
56 size_t retlen;
57 int ret;
58
59 /*
60 * First, let's erase the flash block.
61 */
62
63 init_waitqueue_head(&wait_q);
64 erase.mtd = mtd;
65 erase.callback = erase_callback;
66 erase.addr = pos;
67 erase.len = len;
68 erase.priv = (u_long)&wait_q;
69
70 set_current_state(TASK_INTERRUPTIBLE);
71 add_wait_queue(&wait_q, &wait);
72
73 ret = mtd->erase(mtd, &erase);
74 if (ret) {
75 set_current_state(TASK_RUNNING);
76 remove_wait_queue(&wait_q, &wait);
77 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
78 "on \"%s\" failed\n",
79 pos, len, mtd->name);
80 return ret;
81 }
82
83 schedule(); /* Wait for erase to finish. */
84 remove_wait_queue(&wait_q, &wait);
85
86 /*
87 * Next, writhe data to flash.
88 */
89
90 ret = mtd->write(mtd, pos, len, &retlen, buf);
91 if (ret)
92 return ret;
93 if (retlen != len)
94 return -EIO;
95 return 0;
96 }
97
98
99 static int write_cached_data (struct mtdblk_dev *mtdblk)
100 {
101 struct mtd_info *mtd = mtdblk->mtd;
102 int ret;
103
104 if (mtdblk->cache_state != STATE_DIRTY)
105 return 0;
106
107 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
108 "at 0x%lx, size 0x%x\n", mtd->name,
109 mtdblk->cache_offset, mtdblk->cache_size);
110
111 ret = erase_write (mtd, mtdblk->cache_offset,
112 mtdblk->cache_size, mtdblk->cache_data);
113 if (ret)
114 return ret;
115
116 /*
117 * Here we could argubly set the cache state to STATE_CLEAN.
118 * However this could lead to inconsistency since we will not
119 * be notified if this content is altered on the flash by other
120 * means. Let's declare it empty and leave buffering tasks to
121 * the buffer cache instead.
122 */
123 mtdblk->cache_state = STATE_EMPTY;
124 return 0;
125 }
126
127
128 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
129 int len, const char *buf)
130 {
131 struct mtd_info *mtd = mtdblk->mtd;
132 unsigned int sect_size = mtdblk->cache_size;
133 size_t retlen;
134 int ret;
135
136 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
137 mtd->name, pos, len);
138
139 if (!sect_size)
140 return mtd->write(mtd, pos, len, &retlen, buf);
141
142 while (len > 0) {
143 unsigned long sect_start = (pos/sect_size)*sect_size;
144 unsigned int offset = pos - sect_start;
145 unsigned int size = sect_size - offset;
146 if( size > len )
147 size = len;
148
149 if (size == sect_size) {
150 /*
151 * We are covering a whole sector. Thus there is no
152 * need to bother with the cache while it may still be
153 * useful for other partial writes.
154 */
155 ret = erase_write (mtd, pos, size, buf);
156 if (ret)
157 return ret;
158 } else {
159 /* Partial sector: need to use the cache */
160
161 if (mtdblk->cache_state == STATE_DIRTY &&
162 mtdblk->cache_offset != sect_start) {
163 ret = write_cached_data(mtdblk);
164 if (ret)
165 return ret;
166 }
167
168 if (mtdblk->cache_state == STATE_EMPTY ||
169 mtdblk->cache_offset != sect_start) {
170 /* fill the cache with the current sector */
171 mtdblk->cache_state = STATE_EMPTY;
172 ret = mtd->read(mtd, sect_start, sect_size,
173 &retlen, mtdblk->cache_data);
174 if (ret)
175 return ret;
176 if (retlen != sect_size)
177 return -EIO;
178
179 mtdblk->cache_offset = sect_start;
180 mtdblk->cache_size = sect_size;
181 mtdblk->cache_state = STATE_CLEAN;
182 }
183
184 /* write data to our local cache */
185 memcpy (mtdblk->cache_data + offset, buf, size);
186 mtdblk->cache_state = STATE_DIRTY;
187 }
188
189 buf += size;
190 pos += size;
191 len -= size;
192 }
193
194 return 0;
195 }
196
197
198 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
199 int len, char *buf)
200 {
201 struct mtd_info *mtd = mtdblk->mtd;
202 unsigned int sect_size = mtdblk->cache_size;
203 size_t retlen;
204 int ret;
205
206 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
207 mtd->name, pos, len);
208
209 if (!sect_size)
210 return mtd->read(mtd, pos, len, &retlen, buf);
211
212 while (len > 0) {
213 unsigned long sect_start = (pos/sect_size)*sect_size;
214 unsigned int offset = pos - sect_start;
215 unsigned int size = sect_size - offset;
216 if (size > len)
217 size = len;
218
219 /*
220 * Check if the requested data is already cached
221 * Read the requested amount of data from our internal cache if it
222 * contains what we want, otherwise we read the data directly
223 * from flash.
224 */
225 if (mtdblk->cache_state != STATE_EMPTY &&
226 mtdblk->cache_offset == sect_start) {
227 memcpy (buf, mtdblk->cache_data + offset, size);
228 } else {
229 ret = mtd->read(mtd, pos, size, &retlen, buf);
230 if (ret)
231 return ret;
232 if (retlen != size)
233 return -EIO;
234 }
235
236 buf += size;
237 pos += size;
238 len -= size;
239 }
240
241 return 0;
242 }
243
244 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
245 unsigned long block, char *buf)
246 {
247 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
248 return do_cached_read(mtdblk, block<<9, 512, buf);
249 }
250
251 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
252 unsigned long block, char *buf)
253 {
254 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
255 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
256 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize);
257 if (!mtdblk->cache_data)
258 return -EINTR;
259 /* -EINTR is not really correct, but it is the best match
260 * documented in man 2 write for all cases. We could also
261 * return -EAGAIN sometimes, but why bother?
262 */
263 }
264 return do_cached_write(mtdblk, block<<9, 512, buf);
265 }
266
267 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
268 {
269 struct mtdblk_dev *mtdblk;
270 struct mtd_info *mtd = mbd->mtd;
271 int dev = mbd->devnum;
272
273 DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
274
275 mutex_lock(&mtdblks_lock);
276 if (mtdblks[dev]) {
277 mtdblks[dev]->count++;
278 mutex_unlock(&mtdblks_lock);
279 return 0;
280 }
281
282 /* OK, it's not open. Create cache info for it */
283 mtdblk = kzalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
284 if (!mtdblk) {
285 mutex_unlock(&mtdblks_lock);
286 return -ENOMEM;
287 }
288
289 mtdblk->count = 1;
290 mtdblk->mtd = mtd;
291
292 mutex_init(&mtdblk->cache_mutex);
293 mtdblk->cache_state = STATE_EMPTY;
294 if ( !(mtdblk->mtd->flags & MTD_NO_ERASE) && mtdblk->mtd->erasesize) {
295 mtdblk->cache_size = mtdblk->mtd->erasesize;
296 mtdblk->cache_data = NULL;
297 }
298
299 mtdblks[dev] = mtdblk;
300 mutex_unlock(&mtdblks_lock);
301
302 DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
303
304 return 0;
305 }
306
307 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
308 {
309 int dev = mbd->devnum;
310 struct mtdblk_dev *mtdblk = mtdblks[dev];
311
312 DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
313
314 mutex_lock(&mtdblks_lock);
315
316 mutex_lock(&mtdblk->cache_mutex);
317 write_cached_data(mtdblk);
318 mutex_unlock(&mtdblk->cache_mutex);
319
320 if (!--mtdblk->count) {
321 /* It was the last usage. Free the device */
322 mtdblks[dev] = NULL;
323 if (mtdblk->mtd->sync)
324 mtdblk->mtd->sync(mtdblk->mtd);
325 vfree(mtdblk->cache_data);
326 kfree(mtdblk);
327 }
328
329 mutex_unlock(&mtdblks_lock);
330
331 DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
332
333 return 0;
334 }
335
336 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
337 {
338 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
339
340 mutex_lock(&mtdblk->cache_mutex);
341 write_cached_data(mtdblk);
342 mutex_unlock(&mtdblk->cache_mutex);
343
344 if (mtdblk->mtd->sync)
345 mtdblk->mtd->sync(mtdblk->mtd);
346 return 0;
347 }
348
349 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
350 {
351 struct mtd_blktrans_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
352
353 if (!dev)
354 return;
355
356 dev->mtd = mtd;
357 dev->devnum = mtd->index;
358
359 dev->size = mtd->size >> 9;
360 dev->tr = tr;
361
362 if (!(mtd->flags & MTD_WRITEABLE))
363 dev->readonly = 1;
364
365 add_mtd_blktrans_dev(dev);
366 }
367
368 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
369 {
370 del_mtd_blktrans_dev(dev);
371 kfree(dev);
372 }
373
374 static struct mtd_blktrans_ops mtdblock_tr = {
375 .name = "mtdblock",
376 .major = 31,
377 .part_bits = 0,
378 .blksize = 512,
379 .open = mtdblock_open,
380 .flush = mtdblock_flush,
381 .release = mtdblock_release,
382 .readsect = mtdblock_readsect,
383 .writesect = mtdblock_writesect,
384 .add_mtd = mtdblock_add_mtd,
385 .remove_dev = mtdblock_remove_dev,
386 .owner = THIS_MODULE,
387 };
388
389 static int __init init_mtdblock(void)
390 {
391 mutex_init(&mtdblks_lock);
392
393 return register_mtd_blktrans(&mtdblock_tr);
394 }
395
396 static void __exit cleanup_mtdblock(void)
397 {
398 deregister_mtd_blktrans(&mtdblock_tr);
399 }
400
401 module_init(init_mtdblock);
402 module_exit(cleanup_mtdblock);
403
404
405 MODULE_LICENSE("GPL");
406 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al.");
407 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
408
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