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 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, 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         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@cam.org> et al.");
 407 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");