a052648f6e319c4f58e6d2fb6ffff7bbcaad17f6
[linux-2.6.git] / drivers / mtd / mtdblock.c
1 /*
2  * Direct MTD block device access
3  *
4  * $Id: mtdblock.c,v 1.68 2005/11/07 11:14:20 gleixner Exp $
5  *
6  * (C) 2000-2003 Nicolas Pitre <nico@cam.org>
7  * (C) 1999-2003 David Woodhouse <dwmw2@infradead.org>
8  */
9
10 #include <linux/fs.h>
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/types.h>
17 #include <linux/vmalloc.h>
18
19 #include <linux/mtd/mtd.h>
20 #include <linux/mtd/blktrans.h>
21 #include <linux/mutex.h>
22
23
24 static struct mtdblk_dev {
25         struct mtd_info *mtd;
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 } *mtdblks[MAX_MTD_DEVICES];
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         if (mtdblks[dev]) {
276                 mtdblks[dev]->count++;
277                 return 0;
278         }
279
280         /* OK, it's not open. Create cache info for it */
281         mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
282         if (!mtdblk)
283                 return -ENOMEM;
284
285         memset(mtdblk, 0, sizeof(*mtdblk));
286         mtdblk->count = 1;
287         mtdblk->mtd = mtd;
288
289         mutex_init(&mtdblk->cache_mutex);
290         mtdblk->cache_state = STATE_EMPTY;
291         if ( !(mtdblk->mtd->flags & MTD_NO_ERASE) && mtdblk->mtd->erasesize) {
292                 mtdblk->cache_size = mtdblk->mtd->erasesize;
293                 mtdblk->cache_data = NULL;
294         }
295
296         mtdblks[dev] = mtdblk;
297
298         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
299
300         return 0;
301 }
302
303 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
304 {
305         int dev = mbd->devnum;
306         struct mtdblk_dev *mtdblk = mtdblks[dev];
307
308         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
309
310         mutex_lock(&mtdblk->cache_mutex);
311         write_cached_data(mtdblk);
312         mutex_unlock(&mtdblk->cache_mutex);
313
314         if (!--mtdblk->count) {
315                 /* It was the last usage. Free the device */
316                 mtdblks[dev] = NULL;
317                 if (mtdblk->mtd->sync)
318                         mtdblk->mtd->sync(mtdblk->mtd);
319                 vfree(mtdblk->cache_data);
320                 kfree(mtdblk);
321         }
322         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
323
324         return 0;
325 }
326
327 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
328 {
329         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
330
331         mutex_lock(&mtdblk->cache_mutex);
332         write_cached_data(mtdblk);
333         mutex_unlock(&mtdblk->cache_mutex);
334
335         if (mtdblk->mtd->sync)
336                 mtdblk->mtd->sync(mtdblk->mtd);
337         return 0;
338 }
339
340 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
341 {
342         struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL);
343
344         if (!dev)
345                 return;
346
347         memset(dev, 0, sizeof(*dev));
348
349         dev->mtd = mtd;
350         dev->devnum = mtd->index;
351
352         dev->size = mtd->size >> 9;
353         dev->tr = tr;
354
355         if (!(mtd->flags & MTD_WRITEABLE))
356                 dev->readonly = 1;
357
358         add_mtd_blktrans_dev(dev);
359 }
360
361 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
362 {
363         del_mtd_blktrans_dev(dev);
364         kfree(dev);
365 }
366
367 static struct mtd_blktrans_ops mtdblock_tr = {
368         .name           = "mtdblock",
369         .major          = 31,
370         .part_bits      = 0,
371         .blksize        = 512,
372         .open           = mtdblock_open,
373         .flush          = mtdblock_flush,
374         .release        = mtdblock_release,
375         .readsect       = mtdblock_readsect,
376         .writesect      = mtdblock_writesect,
377         .add_mtd        = mtdblock_add_mtd,
378         .remove_dev     = mtdblock_remove_dev,
379         .owner          = THIS_MODULE,
380 };
381
382 static int __init init_mtdblock(void)
383 {
384         return register_mtd_blktrans(&mtdblock_tr);
385 }
386
387 static void __exit cleanup_mtdblock(void)
388 {
389         deregister_mtd_blktrans(&mtdblock_tr);
390 }
391
392 module_init(init_mtdblock);
393 module_exit(cleanup_mtdblock);
394
395
396 MODULE_LICENSE("GPL");
397 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al.");
398 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");