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");