drivers/mtd/mtdblock.c

   1 /*
   2  * Direct MTD block device access
   3  *
   4  * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
   5  * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20  *
  21  */
  22
  23 #include <linux/fs.h>
  24 #include <linux/init.h>
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/sched.h>
  28 #include <linux/slab.h>
  29 #include <linux/types.h>
  30 #include <linux/vmalloc.h>
  31
  32 #include <linux/mtd/mtd.h>
  33 #include <linux/mtd/blktrans.h>
  34 #include <linux/mutex.h>
  35 #include <linux/major.h>
  36
  37
  38 struct mtdblk_dev {
  39         struct mtd_blktrans_dev mbd;
  40         int count;
  41         struct mutex cache_mutex;
  42         unsigned char *cache_data;
  43         unsigned long cache_offset;
  44         unsigned int cache_size;
  45         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
  46 };
  47
  48 /*
  49  * Cache stuff...
  50  *
  51  * Since typical flash erasable sectors are much larger than what Linux's
  52  * buffer cache can handle, we must implement read-modify-write on flash
  53  * sectors for each block write requests.  To avoid over-erasing flash sectors
  54  * and to speed things up, we locally cache a whole flash sector while it is
  55  * being written to until a different sector is required.
  56  */
  57
  58 static void erase_callback(struct erase_info *done)
  59 {
  60         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
  61         wake_up(wait_q);
  62 }
  63
  64 static int erase_write (struct mtd_info *mtd, unsigned long pos,
  65                         int len, const char *buf)
  66 {
  67         struct erase_info erase;
  68         DECLARE_WAITQUEUE(wait, current);
  69         wait_queue_head_t wait_q;
  70         size_t retlen;
  71         int ret;
  72
  73         /*
  74          * First, let's erase the flash block.
  75          */
  76
  77         init_waitqueue_head(&wait_q);
  78         erase.mtd = mtd;
  79         erase.callback = erase_callback;
  80         erase.addr = pos;
  81         erase.len = len;
  82         erase.priv = (u_long)&wait_q;
  83
  84         set_current_state(TASK_INTERRUPTIBLE);
  85         add_wait_queue(&wait_q, &wait);
  86
  87         ret = mtd_erase(mtd, &erase);
  88         if (ret) {
  89                 set_current_state(TASK_RUNNING);
  90                 remove_wait_queue(&wait_q, &wait);
  91                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
  92                                      "on \"%s\" failed\n",
  93                         pos, len, mtd->name);
  94                 return ret;
  95         }
  96
  97         schedule();  /* Wait for erase to finish. */
  98         remove_wait_queue(&wait_q, &wait);
  99
 100         /*
 101          * Next, write the data to flash.
 102          */
 103
 104         ret = mtd_write(mtd, pos, len, &retlen, buf);
 105         if (ret)
 106                 return ret;
 107         if (retlen != len)
 108                 return -EIO;
 109         return 0;
 110 }
 111
 112
 113 static int write_cached_data (struct mtdblk_dev *mtdblk)
 114 {
 115         struct mtd_info *mtd = mtdblk->mbd.mtd;
 116         int ret;
 117
 118         if (mtdblk->cache_state != STATE_DIRTY)
 119                 return 0;
 120
 121         pr_debug("mtdblock: writing cached data for \"%s\" "
 122                         "at 0x%lx, size 0x%x\n", mtd->name,
 123                         mtdblk->cache_offset, mtdblk->cache_size);
 124
 125         ret = erase_write (mtd, mtdblk->cache_offset,
 126                            mtdblk->cache_size, mtdblk->cache_data);
 127         if (ret)
 128                 return ret;
 129
 130         /*
 131          * Here we could arguably set the cache state to STATE_CLEAN.
 132          * However this could lead to inconsistency since we will not
 133          * be notified if this content is altered on the flash by other
 134          * means.  Let's declare it empty and leave buffering tasks to
 135          * the buffer cache instead.
 136          */
 137         mtdblk->cache_state = STATE_EMPTY;
 138         return 0;
 139 }
 140
 141
 142 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 143                             int len, const char *buf)
 144 {
 145         struct mtd_info *mtd = mtdblk->mbd.mtd;
 146         unsigned int sect_size = mtdblk->cache_size;
 147         size_t retlen;
 148         int ret;
 149
 150         pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
 151                 mtd->name, pos, len);
 152
 153         if (!sect_size)
 154                 return mtd_write(mtd, pos, len, &retlen, buf);
 155
 156         while (len > 0) {
 157                 unsigned long sect_start = (pos/sect_size)*sect_size;
 158                 unsigned int offset = pos - sect_start;
 159                 unsigned int size = sect_size - offset;
 160                 if( size > len )
 161                         size = len;
 162
 163                 if (size == sect_size) {
 164                         /*
 165                          * We are covering a whole sector.  Thus there is no
 166                          * need to bother with the cache while it may still be
 167                          * useful for other partial writes.
 168                          */
 169                         ret = erase_write (mtd, pos, size, buf);
 170                         if (ret)
 171                                 return ret;
 172                 } else {
 173                         /* Partial sector: need to use the cache */
 174
 175                         if (mtdblk->cache_state == STATE_DIRTY &&
 176                             mtdblk->cache_offset != sect_start) {
 177                                 ret = write_cached_data(mtdblk);
 178                                 if (ret)
 179                                         return ret;
 180                         }
 181
 182                         if (mtdblk->cache_state == STATE_EMPTY ||
 183                             mtdblk->cache_offset != sect_start) {
 184                                 /* fill the cache with the current sector */
 185                                 mtdblk->cache_state = STATE_EMPTY;
 186                                 ret = mtd_read(mtd, sect_start, sect_size,
 187                                                &retlen, mtdblk->cache_data);
 188                                 if (ret)
 189                                         return ret;
 190                                 if (retlen != sect_size)
 191                                         return -EIO;
 192
 193                                 mtdblk->cache_offset = sect_start;
 194                                 mtdblk->cache_size = sect_size;
 195                                 mtdblk->cache_state = STATE_CLEAN;
 196                         }
 197
 198                         /* write data to our local cache */
 199                         memcpy (mtdblk->cache_data + offset, buf, size);
 200                         mtdblk->cache_state = STATE_DIRTY;
 201                 }
 202
 203                 buf += size;
 204                 pos += size;
 205                 len -= size;
 206         }
 207
 208         return 0;
 209 }
 210
 211
 212 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 213                            int len, char *buf)
 214 {
 215         struct mtd_info *mtd = mtdblk->mbd.mtd;
 216         unsigned int sect_size = mtdblk->cache_size;
 217         size_t retlen;
 218         int ret;
 219
 220         pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 221                         mtd->name, pos, len);
 222
 223         if (!sect_size)
 224                 return mtd_read(mtd, pos, len, &retlen, buf);
 225
 226         while (len > 0) {
 227                 unsigned long sect_start = (pos/sect_size)*sect_size;
 228                 unsigned int offset = pos - sect_start;
 229                 unsigned int size = sect_size - offset;
 230                 if (size > len)
 231                         size = len;
 232
 233                 /*
 234                  * Check if the requested data is already cached
 235                  * Read the requested amount of data from our internal cache if it
 236                  * contains what we want, otherwise we read the data directly
 237                  * from flash.
 238                  */
 239                 if (mtdblk->cache_state != STATE_EMPTY &&
 240                     mtdblk->cache_offset == sect_start) {
 241                         memcpy (buf, mtdblk->cache_data + offset, size);
 242                 } else {
 243                         ret = mtd_read(mtd, pos, size, &retlen, buf);
 244                         if (ret)
 245                                 return ret;
 246                         if (retlen != size)
 247                                 return -EIO;
 248                 }
 249
 250                 buf += size;
 251                 pos += size;
 252                 len -= size;
 253         }
 254
 255         return 0;
 256 }
 257
 258 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
 259                               unsigned long block, char *buf)
 260 {
 261         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 262         return do_cached_read(mtdblk, block<<9, 512, buf);
 263 }
 264
 265 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
 266                               unsigned long block, char *buf)
 267 {
 268         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 269         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 270                 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
 271                 if (!mtdblk->cache_data)
 272                         return -EINTR;
 273                 /* -EINTR is not really correct, but it is the best match
 274                  * documented in man 2 write for all cases.  We could also
 275                  * return -EAGAIN sometimes, but why bother?
 276                  */
 277         }
 278         return do_cached_write(mtdblk, block<<9, 512, buf);
 279 }
 280
 281 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 282 {
 283         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 284
 285         pr_debug("mtdblock_open\n");
 286
 287         if (mtdblk->count) {
 288                 mtdblk->count++;
 289                 return 0;
 290         }
 291
 292         /* OK, it's not open. Create cache info for it */
 293         mtdblk->count = 1;
 294         mutex_init(&mtdblk->cache_mutex);
 295         mtdblk->cache_state = STATE_EMPTY;
 296         if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
 297                 mtdblk->cache_size = mbd->mtd->erasesize;
 298                 mtdblk->cache_data = NULL;
 299         }
 300
 301         pr_debug("ok\n");
 302
 303         return 0;
 304 }
 305
 306 static void mtdblock_release(struct mtd_blktrans_dev *mbd)
 307 {
 308         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 309
 310         pr_debug("mtdblock_release\n");
 311
 312         mutex_lock(&mtdblk->cache_mutex);
 313         write_cached_data(mtdblk);
 314         mutex_unlock(&mtdblk->cache_mutex);
 315
 316         if (!--mtdblk->count) {
 317                 /*
 318                  * It was the last usage. Free the cache, but only sync if
 319                  * opened for writing.
 320                  */
 321                 if (mbd->file_mode & FMODE_WRITE)
 322                         mtd_sync(mbd->mtd);
 323                 vfree(mtdblk->cache_data);
 324         }
 325
 326         pr_debug("ok\n");
 327 }
 328
 329 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 330 {
 331         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 332
 333         mutex_lock(&mtdblk->cache_mutex);
 334         write_cached_data(mtdblk);
 335         mutex_unlock(&mtdblk->cache_mutex);
 336         mtd_sync(dev->mtd);
 337         return 0;
 338 }
 339
 340 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 341 {
 342         struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 343
 344         if (!dev)
 345                 return;
 346
 347         dev->mbd.mtd = mtd;
 348         dev->mbd.devnum = mtd->index;
 349
 350         dev->mbd.size = mtd->size >> 9;
 351         dev->mbd.tr = tr;
 352
 353         if (!(mtd->flags & MTD_WRITEABLE))
 354                 dev->mbd.readonly = 1;
 355
 356         if (add_mtd_blktrans_dev(&dev->mbd))
 357                 kfree(dev);
 358 }
 359
 360 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 361 {
 362         del_mtd_blktrans_dev(dev);
 363 }
 364
 365 static struct mtd_blktrans_ops mtdblock_tr = {
 366         .name           = "mtdblock",
 367         .major          = MTD_BLOCK_MAJOR,
 368         .part_bits      = 0,
 369         .blksize        = 512,
 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@fluxnic.net> et al.");
 396 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");