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