Merge branch 'master'
[linux-2.6] / 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/config.h>
11 #include <linux/fs.h>
12 #include <linux/init.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/slab.h>
17 #include <linux/types.h>
18 #include <linux/vmalloc.h>
19
20 #include <linux/mtd/mtd.h>
21 #include <linux/mtd/blktrans.h>
22
23 static struct mtdblk_dev {
24         struct mtd_info *mtd;
25         int count;
26         struct semaphore cache_sem;
27         unsigned char *cache_data;
28         unsigned long cache_offset;
29         unsigned int cache_size;
30         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
31 } *mtdblks[MAX_MTD_DEVICES];
32
33 /*
34  * Cache stuff...
35  *
36  * Since typical flash erasable sectors are much larger than what Linux's
37  * buffer cache can handle, we must implement read-modify-write on flash
38  * sectors for each block write requests.  To avoid over-erasing flash sectors
39  * and to speed things up, we locally cache a whole flash sector while it is
40  * being written to until a different sector is required.
41  */
42
43 static void erase_callback(struct erase_info *done)
44 {
45         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
46         wake_up(wait_q);
47 }
48
49 static int erase_write (struct mtd_info *mtd, unsigned long pos,
50                         int len, const char *buf)
51 {
52         struct erase_info erase;
53         DECLARE_WAITQUEUE(wait, current);
54         wait_queue_head_t wait_q;
55         size_t retlen;
56         int ret;
57
58         /*
59          * First, let's erase the flash block.
60          */
61
62         init_waitqueue_head(&wait_q);
63         erase.mtd = mtd;
64         erase.callback = erase_callback;
65         erase.addr = pos;
66         erase.len = len;
67         erase.priv = (u_long)&wait_q;
68
69         set_current_state(TASK_INTERRUPTIBLE);
70         add_wait_queue(&wait_q, &wait);
71
72         ret = MTD_ERASE(mtd, &erase);
73         if (ret) {
74                 set_current_state(TASK_RUNNING);
75                 remove_wait_queue(&wait_q, &wait);
76                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
77                                      "on \"%s\" failed\n",
78                         pos, len, mtd->name);
79                 return ret;
80         }
81
82         schedule();  /* Wait for erase to finish. */
83         remove_wait_queue(&wait_q, &wait);
84
85         /*
86          * Next, writhe data to flash.
87          */
88
89         ret = MTD_WRITE (mtd, pos, len, &retlen, buf);
90         if (ret)
91                 return ret;
92         if (retlen != len)
93                 return -EIO;
94         return 0;
95 }
96
97
98 static int write_cached_data (struct mtdblk_dev *mtdblk)
99 {
100         struct mtd_info *mtd = mtdblk->mtd;
101         int ret;
102
103         if (mtdblk->cache_state != STATE_DIRTY)
104                 return 0;
105
106         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
107                         "at 0x%lx, size 0x%x\n", mtd->name,
108                         mtdblk->cache_offset, mtdblk->cache_size);
109
110         ret = erase_write (mtd, mtdblk->cache_offset,
111                            mtdblk->cache_size, mtdblk->cache_data);
112         if (ret)
113                 return ret;
114
115         /*
116          * Here we could argubly set the cache state to STATE_CLEAN.
117          * However this could lead to inconsistency since we will not
118          * be notified if this content is altered on the flash by other
119          * means.  Let's declare it empty and leave buffering tasks to
120          * the buffer cache instead.
121          */
122         mtdblk->cache_state = STATE_EMPTY;
123         return 0;
124 }
125
126
127 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
128                             int len, const char *buf)
129 {
130         struct mtd_info *mtd = mtdblk->mtd;
131         unsigned int sect_size = mtdblk->cache_size;
132         size_t retlen;
133         int ret;
134
135         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
136                 mtd->name, pos, len);
137
138         if (!sect_size)
139                 return MTD_WRITE (mtd, pos, len, &retlen, buf);
140
141         while (len > 0) {
142                 unsigned long sect_start = (pos/sect_size)*sect_size;
143                 unsigned int offset = pos - sect_start;
144                 unsigned int size = sect_size - offset;
145                 if( size > len )
146                         size = len;
147
148                 if (size == sect_size) {
149                         /*
150                          * We are covering a whole sector.  Thus there is no
151                          * need to bother with the cache while it may still be
152                          * useful for other partial writes.
153                          */
154                         ret = erase_write (mtd, pos, size, buf);
155                         if (ret)
156                                 return ret;
157                 } else {
158                         /* Partial sector: need to use the cache */
159
160                         if (mtdblk->cache_state == STATE_DIRTY &&
161                             mtdblk->cache_offset != sect_start) {
162                                 ret = write_cached_data(mtdblk);
163                                 if (ret)
164                                         return ret;
165                         }
166
167                         if (mtdblk->cache_state == STATE_EMPTY ||
168                             mtdblk->cache_offset != sect_start) {
169                                 /* fill the cache with the current sector */
170                                 mtdblk->cache_state = STATE_EMPTY;
171                                 ret = MTD_READ(mtd, sect_start, sect_size, &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 = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
280         if (!mtdblk)
281                 return -ENOMEM;
282
283         memset(mtdblk, 0, sizeof(*mtdblk));
284         mtdblk->count = 1;
285         mtdblk->mtd = mtd;
286
287         init_MUTEX (&mtdblk->cache_sem);
288         mtdblk->cache_state = STATE_EMPTY;
289         if ((mtdblk->mtd->flags & MTD_CAP_RAM) != MTD_CAP_RAM &&
290             mtdblk->mtd->erasesize) {
291                 mtdblk->cache_size = mtdblk->mtd->erasesize;
292                 mtdblk->cache_data = NULL;
293         }
294
295         mtdblks[dev] = mtdblk;
296
297         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
298
299         return 0;
300 }
301
302 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
303 {
304         int dev = mbd->devnum;
305         struct mtdblk_dev *mtdblk = mtdblks[dev];
306
307         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
308
309         down(&mtdblk->cache_sem);
310         write_cached_data(mtdblk);
311         up(&mtdblk->cache_sem);
312
313         if (!--mtdblk->count) {
314                 /* It was the last usage. Free the device */
315                 mtdblks[dev] = NULL;
316                 if (mtdblk->mtd->sync)
317                         mtdblk->mtd->sync(mtdblk->mtd);
318                 vfree(mtdblk->cache_data);
319                 kfree(mtdblk);
320         }
321         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
322
323         return 0;
324 }
325
326 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
327 {
328         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
329
330         down(&mtdblk->cache_sem);
331         write_cached_data(mtdblk);
332         up(&mtdblk->cache_sem);
333
334         if (mtdblk->mtd->sync)
335                 mtdblk->mtd->sync(mtdblk->mtd);
336         return 0;
337 }
338
339 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
340 {
341         struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL);
342
343         if (!dev)
344                 return;
345
346         memset(dev, 0, sizeof(*dev));
347
348         dev->mtd = mtd;
349         dev->devnum = mtd->index;
350         dev->blksize = 512;
351         dev->size = mtd->size >> 9;
352         dev->tr = tr;
353
354         if (!(mtd->flags & MTD_WRITEABLE))
355                 dev->readonly = 1;
356
357         add_mtd_blktrans_dev(dev);
358 }
359
360 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
361 {
362         del_mtd_blktrans_dev(dev);
363         kfree(dev);
364 }
365
366 static struct mtd_blktrans_ops mtdblock_tr = {
367         .name           = "mtdblock",
368         .major          = 31,
369         .part_bits      = 0,
370         .open           = mtdblock_open,
371         .flush          = mtdblock_flush,
372         .release        = mtdblock_release,
373         .readsect       = mtdblock_readsect,
374         .writesect      = mtdblock_writesect,
375         .add_mtd        = mtdblock_add_mtd,
376         .remove_dev     = mtdblock_remove_dev,
377         .owner          = THIS_MODULE,
378 };
379
380 static int __init init_mtdblock(void)
381 {
382         return register_mtd_blktrans(&mtdblock_tr);
383 }
384
385 static void __exit cleanup_mtdblock(void)
386 {
387         deregister_mtd_blktrans(&mtdblock_tr);
388 }
389
390 module_init(init_mtdblock);
391 module_exit(cleanup_mtdblock);
392
393
394 MODULE_LICENSE("GPL");
395 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al.");
396 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");