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 #include <linux/mutex.h>
  23
  24
  25 static struct mtdblk_dev {
  26         struct mtd_info *mtd;
  27         int count;
  28         struct mutex cache_mutex;
  29         unsigned char *cache_data;
  30         unsigned long cache_offset;
  31         unsigned int cache_size;
  32         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
  33 } *mtdblks[MAX_MTD_DEVICES];
  34
  35 /*
  36  * Cache stuff...
  37  *
  38  * Since typical flash erasable sectors are much larger than what Linux's
  39  * buffer cache can handle, we must implement read-modify-write on flash
  40  * sectors for each block write requests.  To avoid over-erasing flash sectors
  41  * and to speed things up, we locally cache a whole flash sector while it is
  42  * being written to until a different sector is required.
  43  */
  44
  45 static void erase_callback(struct erase_info *done)
  46 {
  47         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
  48         wake_up(wait_q);
  49 }
  50
  51 static int erase_write (struct mtd_info *mtd, unsigned long pos,
  52                         int len, const char *buf)
  53 {
  54         struct erase_info erase;
  55         DECLARE_WAITQUEUE(wait, current);
  56         wait_queue_head_t wait_q;
  57         size_t retlen;
  58         int ret;
  59
  60         /*
  61          * First, let's erase the flash block.
  62          */
  63
  64         init_waitqueue_head(&wait_q);
  65         erase.mtd = mtd;
  66         erase.callback = erase_callback;
  67         erase.addr = pos;
  68         erase.len = len;
  69         erase.priv = (u_long)&wait_q;
  70
  71         set_current_state(TASK_INTERRUPTIBLE);
  72         add_wait_queue(&wait_q, &wait);
  73
  74         ret = mtd->erase(mtd, &erase);
  75         if (ret) {
  76                 set_current_state(TASK_RUNNING);
  77                 remove_wait_queue(&wait_q, &wait);
  78                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
  79                                      "on \"%s\" failed\n",
  80                         pos, len, mtd->name);
  81                 return ret;
  82         }
  83
  84         schedule();  /* Wait for erase to finish. */
  85         remove_wait_queue(&wait_q, &wait);
  86
  87         /*
  88          * Next, writhe data to flash.
  89          */
  90
  91         ret = mtd->write(mtd, pos, len, &retlen, buf);
  92         if (ret)
  93                 return ret;
  94         if (retlen != len)
  95                 return -EIO;
  96         return 0;
  97 }
  98
  99
 100 static int write_cached_data (struct mtdblk_dev *mtdblk)
 101 {
 102         struct mtd_info *mtd = mtdblk->mtd;
 103         int ret;
 104
 105         if (mtdblk->cache_state != STATE_DIRTY)
 106                 return 0;
 107
 108         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
 109                         "at 0x%lx, size 0x%x\n", mtd->name,
 110                         mtdblk->cache_offset, mtdblk->cache_size);
 111
 112         ret = erase_write (mtd, mtdblk->cache_offset,
 113                            mtdblk->cache_size, mtdblk->cache_data);
 114         if (ret)
 115                 return ret;
 116
 117         /*
 118          * Here we could argubly set the cache state to STATE_CLEAN.
 119          * However this could lead to inconsistency since we will not
 120          * be notified if this content is altered on the flash by other
 121          * means.  Let's declare it empty and leave buffering tasks to
 122          * the buffer cache instead.
 123          */
 124         mtdblk->cache_state = STATE_EMPTY;
 125         return 0;
 126 }
 127
 128
 129 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 130                             int len, const char *buf)
 131 {
 132         struct mtd_info *mtd = mtdblk->mtd;
 133         unsigned int sect_size = mtdblk->cache_size;
 134         size_t retlen;
 135         int ret;
 136
 137         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
 138                 mtd->name, pos, len);
 139
 140         if (!sect_size)
 141                 return mtd->write(mtd, pos, len, &retlen, buf);
 142
 143         while (len > 0) {
 144                 unsigned long sect_start = (pos/sect_size)*sect_size;
 145                 unsigned int offset = pos - sect_start;
 146                 unsigned int size = sect_size - offset;
 147                 if( size > len )
 148                         size = len;
 149
 150                 if (size == sect_size) {
 151                         /*
 152                          * We are covering a whole sector.  Thus there is no
 153                          * need to bother with the cache while it may still be
 154                          * useful for other partial writes.
 155                          */
 156                         ret = erase_write (mtd, pos, size, buf);
 157                         if (ret)
 158                                 return ret;
 159                 } else {
 160                         /* Partial sector: need to use the cache */
 161
 162                         if (mtdblk->cache_state == STATE_DIRTY &&
 163                             mtdblk->cache_offset != sect_start) {
 164                                 ret = write_cached_data(mtdblk);
 165                                 if (ret)
 166                                         return ret;
 167                         }
 168
 169                         if (mtdblk->cache_state == STATE_EMPTY ||
 170                             mtdblk->cache_offset != sect_start) {
 171                                 /* fill the cache with the current sector */
 172                                 mtdblk->cache_state = STATE_EMPTY;
 173                                 ret = mtd->read(mtd, sect_start, sect_size,
 174                                                 &retlen, mtdblk->cache_data);
 175                                 if (ret)
 176                                         return ret;
 177                                 if (retlen != sect_size)
 178                                         return -EIO;
 179
 180                                 mtdblk->cache_offset = sect_start;
 181                                 mtdblk->cache_size = sect_size;
 182                                 mtdblk->cache_state = STATE_CLEAN;
 183                         }
 184
 185                         /* write data to our local cache */
 186                         memcpy (mtdblk->cache_data + offset, buf, size);
 187                         mtdblk->cache_state = STATE_DIRTY;
 188                 }
 189
 190                 buf += size;
 191                 pos += size;
 192                 len -= size;
 193         }
 194
 195         return 0;
 196 }
 197
 198
 199 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 200                            int len, char *buf)
 201 {
 202         struct mtd_info *mtd = mtdblk->mtd;
 203         unsigned int sect_size = mtdblk->cache_size;
 204         size_t retlen;
 205         int ret;
 206
 207         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 208                         mtd->name, pos, len);
 209
 210         if (!sect_size)
 211                 return mtd->read(mtd, pos, len, &retlen, buf);
 212
 213         while (len > 0) {
 214                 unsigned long sect_start = (pos/sect_size)*sect_size;
 215                 unsigned int offset = pos - sect_start;
 216                 unsigned int size = sect_size - offset;
 217                 if (size > len)
 218                         size = len;
 219
 220                 /*
 221                  * Check if the requested data is already cached
 222                  * Read the requested amount of data from our internal cache if it
 223                  * contains what we want, otherwise we read the data directly
 224                  * from flash.
 225                  */
 226                 if (mtdblk->cache_state != STATE_EMPTY &&
 227                     mtdblk->cache_offset == sect_start) {
 228                         memcpy (buf, mtdblk->cache_data + offset, size);
 229                 } else {
 230                         ret = mtd->read(mtd, pos, size, &retlen, buf);
 231                         if (ret)
 232                                 return ret;
 233                         if (retlen != size)
 234                                 return -EIO;
 235                 }
 236
 237                 buf += size;
 238                 pos += size;
 239                 len -= size;
 240         }
 241
 242         return 0;
 243 }
 244
 245 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
 246                               unsigned long block, char *buf)
 247 {
 248         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 249         return do_cached_read(mtdblk, block<<9, 512, buf);
 250 }
 251
 252 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
 253                               unsigned long block, char *buf)
 254 {
 255         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 256         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 257                 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize);
 258                 if (!mtdblk->cache_data)
 259                         return -EINTR;
 260                 /* -EINTR is not really correct, but it is the best match
 261                  * documented in man 2 write for all cases.  We could also
 262                  * return -EAGAIN sometimes, but why bother?
 263                  */
 264         }
 265         return do_cached_write(mtdblk, block<<9, 512, buf);
 266 }
 267
 268 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 269 {
 270         struct mtdblk_dev *mtdblk;
 271         struct mtd_info *mtd = mbd->mtd;
 272         int dev = mbd->devnum;
 273
 274         DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
 275
 276         if (mtdblks[dev]) {
 277                 mtdblks[dev]->count++;
 278                 return 0;
 279         }
 280
 281         /* OK, it's not open. Create cache info for it */
 282         mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
 283         if (!mtdblk)
 284                 return -ENOMEM;
 285
 286         memset(mtdblk, 0, sizeof(*mtdblk));
 287         mtdblk->count = 1;
 288         mtdblk->mtd = mtd;
 289
 290         mutex_init(&mtdblk->cache_mutex);
 291         mtdblk->cache_state = STATE_EMPTY;
 292         if ( !(mtdblk->mtd->flags & MTD_NO_ERASE) && mtdblk->mtd->erasesize) {
 293                 mtdblk->cache_size = mtdblk->mtd->erasesize;
 294                 mtdblk->cache_data = NULL;
 295         }
 296
 297         mtdblks[dev] = mtdblk;
 298
 299         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 300
 301         return 0;
 302 }
 303
 304 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 305 {
 306         int dev = mbd->devnum;
 307         struct mtdblk_dev *mtdblk = mtdblks[dev];
 308
 309         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
 310
 311         mutex_lock(&mtdblk->cache_mutex);
 312         write_cached_data(mtdblk);
 313         mutex_unlock(&mtdblk->cache_mutex);
 314
 315         if (!--mtdblk->count) {
 316                 /* It was the last usage. Free the device */
 317                 mtdblks[dev] = NULL;
 318                 if (mtdblk->mtd->sync)
 319                         mtdblk->mtd->sync(mtdblk->mtd);
 320                 vfree(mtdblk->cache_data);
 321                 kfree(mtdblk);
 322         }
 323         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 324
 325         return 0;
 326 }
 327
 328 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 329 {
 330         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 331
 332         mutex_lock(&mtdblk->cache_mutex);
 333         write_cached_data(mtdblk);
 334         mutex_unlock(&mtdblk->cache_mutex);
 335
 336         if (mtdblk->mtd->sync)
 337                 mtdblk->mtd->sync(mtdblk->mtd);
 338         return 0;
 339 }
 340
 341 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 342 {
 343         struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL);
 344
 345         if (!dev)
 346                 return;
 347
 348         memset(dev, 0, sizeof(*dev));
 349
 350         dev->mtd = mtd;
 351         dev->devnum = mtd->index;
 352         dev->blksize = 512;
 353         dev->size = mtd->size >> 9;
 354         dev->tr = tr;
 355
 356         if (!(mtd->flags & MTD_WRITEABLE))
 357                 dev->readonly = 1;
 358
 359         add_mtd_blktrans_dev(dev);
 360 }
 361
 362 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 363 {
 364         del_mtd_blktrans_dev(dev);
 365         kfree(dev);
 366 }
 367
 368 static struct mtd_blktrans_ops mtdblock_tr = {
 369         .name           = "mtdblock",
 370         .major          = 31,
 371         .part_bits      = 0,
 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");