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1 | /* |
2 | * Direct MTD block device access |
3 | * |
4 | * (C) 2000-2003 Nicolas Pitre <nico@fluxnic.net> |
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, write the 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@fluxnic.net> et al."); |
407 | MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); |
408 |
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