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");