Fix common misspellings
[linux-2.6.git] / drivers / mtd / mtdblock.c
1 /*
2  * Direct MTD block device access
3  *
4  * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
5  * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
20  *
21  */
22
23 #include <linux/fs.h>
24 #include <linux/init.h>
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/sched.h>
28 #include <linux/slab.h>
29 #include <linux/types.h>
30 #include <linux/vmalloc.h>
31
32 #include <linux/mtd/mtd.h>
33 #include <linux/mtd/blktrans.h>
34 #include <linux/mutex.h>
35
36
37 struct mtdblk_dev {
38         struct mtd_blktrans_dev mbd;
39         int count;
40         struct mutex cache_mutex;
41         unsigned char *cache_data;
42         unsigned long cache_offset;
43         unsigned int cache_size;
44         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
45 };
46
47 static struct mutex mtdblks_lock;
48
49 /*
50  * Cache stuff...
51  *
52  * Since typical flash erasable sectors are much larger than what Linux's
53  * buffer cache can handle, we must implement read-modify-write on flash
54  * sectors for each block write requests.  To avoid over-erasing flash sectors
55  * and to speed things up, we locally cache a whole flash sector while it is
56  * being written to until a different sector is required.
57  */
58
59 static void erase_callback(struct erase_info *done)
60 {
61         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
62         wake_up(wait_q);
63 }
64
65 static int erase_write (struct mtd_info *mtd, unsigned long pos,
66                         int len, const char *buf)
67 {
68         struct erase_info erase;
69         DECLARE_WAITQUEUE(wait, current);
70         wait_queue_head_t wait_q;
71         size_t retlen;
72         int ret;
73
74         /*
75          * First, let's erase the flash block.
76          */
77
78         init_waitqueue_head(&wait_q);
79         erase.mtd = mtd;
80         erase.callback = erase_callback;
81         erase.addr = pos;
82         erase.len = len;
83         erase.priv = (u_long)&wait_q;
84
85         set_current_state(TASK_INTERRUPTIBLE);
86         add_wait_queue(&wait_q, &wait);
87
88         ret = mtd->erase(mtd, &erase);
89         if (ret) {
90                 set_current_state(TASK_RUNNING);
91                 remove_wait_queue(&wait_q, &wait);
92                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
93                                      "on \"%s\" failed\n",
94                         pos, len, mtd->name);
95                 return ret;
96         }
97
98         schedule();  /* Wait for erase to finish. */
99         remove_wait_queue(&wait_q, &wait);
100
101         /*
102          * Next, write the data to flash.
103          */
104
105         ret = mtd->write(mtd, pos, len, &retlen, buf);
106         if (ret)
107                 return ret;
108         if (retlen != len)
109                 return -EIO;
110         return 0;
111 }
112
113
114 static int write_cached_data (struct mtdblk_dev *mtdblk)
115 {
116         struct mtd_info *mtd = mtdblk->mbd.mtd;
117         int ret;
118
119         if (mtdblk->cache_state != STATE_DIRTY)
120                 return 0;
121
122         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
123                         "at 0x%lx, size 0x%x\n", mtd->name,
124                         mtdblk->cache_offset, mtdblk->cache_size);
125
126         ret = erase_write (mtd, mtdblk->cache_offset,
127                            mtdblk->cache_size, mtdblk->cache_data);
128         if (ret)
129                 return ret;
130
131         /*
132          * Here we could arguably set the cache state to STATE_CLEAN.
133          * However this could lead to inconsistency since we will not
134          * be notified if this content is altered on the flash by other
135          * means.  Let's declare it empty and leave buffering tasks to
136          * the buffer cache instead.
137          */
138         mtdblk->cache_state = STATE_EMPTY;
139         return 0;
140 }
141
142
143 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
144                             int len, const char *buf)
145 {
146         struct mtd_info *mtd = mtdblk->mbd.mtd;
147         unsigned int sect_size = mtdblk->cache_size;
148         size_t retlen;
149         int ret;
150
151         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
152                 mtd->name, pos, len);
153
154         if (!sect_size)
155                 return mtd->write(mtd, pos, len, &retlen, buf);
156
157         while (len > 0) {
158                 unsigned long sect_start = (pos/sect_size)*sect_size;
159                 unsigned int offset = pos - sect_start;
160                 unsigned int size = sect_size - offset;
161                 if( size > len )
162                         size = len;
163
164                 if (size == sect_size) {
165                         /*
166                          * We are covering a whole sector.  Thus there is no
167                          * need to bother with the cache while it may still be
168                          * useful for other partial writes.
169                          */
170                         ret = erase_write (mtd, pos, size, buf);
171                         if (ret)
172                                 return ret;
173                 } else {
174                         /* Partial sector: need to use the cache */
175
176                         if (mtdblk->cache_state == STATE_DIRTY &&
177                             mtdblk->cache_offset != sect_start) {
178                                 ret = write_cached_data(mtdblk);
179                                 if (ret)
180                                         return ret;
181                         }
182
183                         if (mtdblk->cache_state == STATE_EMPTY ||
184                             mtdblk->cache_offset != sect_start) {
185                                 /* fill the cache with the current sector */
186                                 mtdblk->cache_state = STATE_EMPTY;
187                                 ret = mtd->read(mtd, sect_start, sect_size,
188                                                 &retlen, mtdblk->cache_data);
189                                 if (ret)
190                                         return ret;
191                                 if (retlen != sect_size)
192                                         return -EIO;
193
194                                 mtdblk->cache_offset = sect_start;
195                                 mtdblk->cache_size = sect_size;
196                                 mtdblk->cache_state = STATE_CLEAN;
197                         }
198
199                         /* write data to our local cache */
200                         memcpy (mtdblk->cache_data + offset, buf, size);
201                         mtdblk->cache_state = STATE_DIRTY;
202                 }
203
204                 buf += size;
205                 pos += size;
206                 len -= size;
207         }
208
209         return 0;
210 }
211
212
213 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
214                            int len, char *buf)
215 {
216         struct mtd_info *mtd = mtdblk->mbd.mtd;
217         unsigned int sect_size = mtdblk->cache_size;
218         size_t retlen;
219         int ret;
220
221         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
222                         mtd->name, pos, len);
223
224         if (!sect_size)
225                 return mtd->read(mtd, pos, len, &retlen, buf);
226
227         while (len > 0) {
228                 unsigned long sect_start = (pos/sect_size)*sect_size;
229                 unsigned int offset = pos - sect_start;
230                 unsigned int size = sect_size - offset;
231                 if (size > len)
232                         size = len;
233
234                 /*
235                  * Check if the requested data is already cached
236                  * Read the requested amount of data from our internal cache if it
237                  * contains what we want, otherwise we read the data directly
238                  * from flash.
239                  */
240                 if (mtdblk->cache_state != STATE_EMPTY &&
241                     mtdblk->cache_offset == sect_start) {
242                         memcpy (buf, mtdblk->cache_data + offset, size);
243                 } else {
244                         ret = mtd->read(mtd, pos, size, &retlen, buf);
245                         if (ret)
246                                 return ret;
247                         if (retlen != size)
248                                 return -EIO;
249                 }
250
251                 buf += size;
252                 pos += size;
253                 len -= size;
254         }
255
256         return 0;
257 }
258
259 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
260                               unsigned long block, char *buf)
261 {
262         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
263         return do_cached_read(mtdblk, block<<9, 512, buf);
264 }
265
266 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
267                               unsigned long block, char *buf)
268 {
269         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
270         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
271                 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
272                 if (!mtdblk->cache_data)
273                         return -EINTR;
274                 /* -EINTR is not really correct, but it is the best match
275                  * documented in man 2 write for all cases.  We could also
276                  * return -EAGAIN sometimes, but why bother?
277                  */
278         }
279         return do_cached_write(mtdblk, block<<9, 512, buf);
280 }
281
282 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
283 {
284         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
285
286         DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
287
288         mutex_lock(&mtdblks_lock);
289         if (mtdblk->count) {
290                 mtdblk->count++;
291                 mutex_unlock(&mtdblks_lock);
292                 return 0;
293         }
294
295         /* OK, it's not open. Create cache info for it */
296         mtdblk->count = 1;
297         mutex_init(&mtdblk->cache_mutex);
298         mtdblk->cache_state = STATE_EMPTY;
299         if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
300                 mtdblk->cache_size = mbd->mtd->erasesize;
301                 mtdblk->cache_data = NULL;
302         }
303
304         mutex_unlock(&mtdblks_lock);
305
306         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
307
308         return 0;
309 }
310
311 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
312 {
313         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
314
315         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
316
317         mutex_lock(&mtdblks_lock);
318
319         mutex_lock(&mtdblk->cache_mutex);
320         write_cached_data(mtdblk);
321         mutex_unlock(&mtdblk->cache_mutex);
322
323         if (!--mtdblk->count) {
324                 /* It was the last usage. Free the cache */
325                 if (mbd->mtd->sync)
326                         mbd->mtd->sync(mbd->mtd);
327                 vfree(mtdblk->cache_data);
328         }
329
330         mutex_unlock(&mtdblks_lock);
331
332         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
333
334         return 0;
335 }
336
337 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
338 {
339         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
340
341         mutex_lock(&mtdblk->cache_mutex);
342         write_cached_data(mtdblk);
343         mutex_unlock(&mtdblk->cache_mutex);
344
345         if (dev->mtd->sync)
346                 dev->mtd->sync(dev->mtd);
347         return 0;
348 }
349
350 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
351 {
352         struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
353
354         if (!dev)
355                 return;
356
357         dev->mbd.mtd = mtd;
358         dev->mbd.devnum = mtd->index;
359
360         dev->mbd.size = mtd->size >> 9;
361         dev->mbd.tr = tr;
362
363         if (!(mtd->flags & MTD_WRITEABLE))
364                 dev->mbd.readonly = 1;
365
366         if (add_mtd_blktrans_dev(&dev->mbd))
367                 kfree(dev);
368 }
369
370 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
371 {
372         del_mtd_blktrans_dev(dev);
373 }
374
375 static struct mtd_blktrans_ops mtdblock_tr = {
376         .name           = "mtdblock",
377         .major          = 31,
378         .part_bits      = 0,
379         .blksize        = 512,
380         .open           = mtdblock_open,
381         .flush          = mtdblock_flush,
382         .release        = mtdblock_release,
383         .readsect       = mtdblock_readsect,
384         .writesect      = mtdblock_writesect,
385         .add_mtd        = mtdblock_add_mtd,
386         .remove_dev     = mtdblock_remove_dev,
387         .owner          = THIS_MODULE,
388 };
389
390 static int __init init_mtdblock(void)
391 {
392         mutex_init(&mtdblks_lock);
393
394         return register_mtd_blktrans(&mtdblock_tr);
395 }
396
397 static void __exit cleanup_mtdblock(void)
398 {
399         deregister_mtd_blktrans(&mtdblock_tr);
400 }
401
402 module_init(init_mtdblock);
403 module_exit(cleanup_mtdblock);
404
405
406 MODULE_LICENSE("GPL");
407 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
408 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");