drivers/mtd/mtdblock.c

   1 /*
   2  * Direct MTD block device access
   3  *
   4  * (C) 2000-2003 Nicolas Pitre <nico@fluxnic.net>
   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 struct mtdblk_dev {
  23         struct mtd_blktrans_dev mbd;
  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 };
  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, write the 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->mbd.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->mbd.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->mbd.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 = container_of(dev, struct mtdblk_dev, mbd);
 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 = container_of(dev, struct mtdblk_dev, mbd);
 255         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 256                 mtdblk->cache_data = vmalloc(mtdblk->mbd.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 = container_of(mbd, struct mtdblk_dev, mbd);
 270
 271         DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
 272
 273         mutex_lock(&mtdblks_lock);
 274         if (mtdblk->count) {
 275                 mtdblk->count++;
 276                 mutex_unlock(&mtdblks_lock);
 277                 return 0;
 278         }
 279
 280         /* OK, it's not open. Create cache info for it */
 281         mtdblk->count = 1;
 282         mutex_init(&mtdblk->cache_mutex);
 283         mtdblk->cache_state = STATE_EMPTY;
 284         if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
 285                 mtdblk->cache_size = mbd->mtd->erasesize;
 286                 mtdblk->cache_data = NULL;
 287         }
 288
 289         mutex_unlock(&mtdblks_lock);
 290
 291         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 292
 293         return 0;
 294 }
 295
 296 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 297 {
 298         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 299
 300         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
 301
 302         mutex_lock(&mtdblks_lock);
 303
 304         mutex_lock(&mtdblk->cache_mutex);
 305         write_cached_data(mtdblk);
 306         mutex_unlock(&mtdblk->cache_mutex);
 307
 308         if (!--mtdblk->count) {
 309                 /* It was the last usage. Free the cache */
 310                 if (mbd->mtd->sync)
 311                         mbd->mtd->sync(mbd->mtd);
 312                 vfree(mtdblk->cache_data);
 313         }
 314
 315         mutex_unlock(&mtdblks_lock);
 316
 317         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 318
 319         return 0;
 320 }
 321
 322 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 323 {
 324         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 325
 326         mutex_lock(&mtdblk->cache_mutex);
 327         write_cached_data(mtdblk);
 328         mutex_unlock(&mtdblk->cache_mutex);
 329
 330         if (dev->mtd->sync)
 331                 dev->mtd->sync(dev->mtd);
 332         return 0;
 333 }
 334
 335 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 336 {
 337         struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 338
 339         if (!dev)
 340                 return;
 341
 342         dev->mbd.mtd = mtd;
 343         dev->mbd.devnum = mtd->index;
 344
 345         dev->mbd.size = mtd->size >> 9;
 346         dev->mbd.tr = tr;
 347
 348         if (!(mtd->flags & MTD_WRITEABLE))
 349                 dev->mbd.readonly = 1;
 350
 351         if (add_mtd_blktrans_dev(&dev->mbd))
 352                 kfree(dev);
 353 }
 354
 355 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 356 {
 357         del_mtd_blktrans_dev(dev);
 358 }
 359
 360 static struct mtd_blktrans_ops mtdblock_tr = {
 361         .name           = "mtdblock",
 362         .major          = 31,
 363         .part_bits      = 0,
 364         .blksize        = 512,
 365         .open           = mtdblock_open,
 366         .flush          = mtdblock_flush,
 367         .release        = mtdblock_release,
 368         .readsect       = mtdblock_readsect,
 369         .writesect      = mtdblock_writesect,
 370         .add_mtd        = mtdblock_add_mtd,
 371         .remove_dev     = mtdblock_remove_dev,
 372         .owner          = THIS_MODULE,
 373 };
 374
 375 static int __init init_mtdblock(void)
 376 {
 377         mutex_init(&mtdblks_lock);
 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@fluxnic.net> et al.");
 393 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");