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
  36
  37 struct mtdblk_dev {
  38         struct mtd_blktrans_dev mbd;
  39         int count;
  40         struct mutex cache_mutex;
  41         unsigned char *cache_data;
  42         unsigned long cache_offset;
  43         unsigned int cache_size;
  44         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
  45 };
  46
  47 static DEFINE_MUTEX(mtdblks_lock);
  48
  49 /*
  50  * Cache stuff...
  51  *
  52  * Since typical flash erasable sectors are much larger than what Linux's
  53  * buffer cache can handle, we must implement read-modify-write on flash
  54  * sectors for each block write requests.  To avoid over-erasing flash sectors
  55  * and to speed things up, we locally cache a whole flash sector while it is
  56  * being written to until a different sector is required.
  57  */
  58
  59 static void erase_callback(struct erase_info *done)
  60 {
  61         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
  62         wake_up(wait_q);
  63 }
  64
  65 static int erase_write (struct mtd_info *mtd, unsigned long pos,
  66                         int len, const char *buf)
  67 {
  68         struct erase_info erase;
  69         DECLARE_WAITQUEUE(wait, current);
  70         wait_queue_head_t wait_q;
  71         size_t retlen;
  72         int ret;
  73
  74         /*
  75          * First, let's erase the flash block.
  76          */
  77
  78         init_waitqueue_head(&wait_q);
  79         erase.mtd = mtd;
  80         erase.callback = erase_callback;
  81         erase.addr = pos;
  82         erase.len = len;
  83         erase.priv = (u_long)&wait_q;
  84
  85         set_current_state(TASK_INTERRUPTIBLE);
  86         add_wait_queue(&wait_q, &wait);
  87
  88         ret = mtd->erase(mtd, &erase);
  89         if (ret) {
  90                 set_current_state(TASK_RUNNING);
  91                 remove_wait_queue(&wait_q, &wait);
  92                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
  93                                      "on \"%s\" failed\n",
  94                         pos, len, mtd->name);
  95                 return ret;
  96         }
  97
  98         schedule();  /* Wait for erase to finish. */
  99         remove_wait_queue(&wait_q, &wait);
 100
 101         /*
 102          * Next, write the data to flash.
 103          */
 104
 105         ret = mtd->write(mtd, pos, len, &retlen, buf);
 106         if (ret)
 107                 return ret;
 108         if (retlen != len)
 109                 return -EIO;
 110         return 0;
 111 }
 112
 113
 114 static int write_cached_data (struct mtdblk_dev *mtdblk)
 115 {
 116         struct mtd_info *mtd = mtdblk->mbd.mtd;
 117         int ret;
 118
 119         if (mtdblk->cache_state != STATE_DIRTY)
 120                 return 0;
 121
 122         pr_debug("mtdblock: writing cached data for \"%s\" "
 123                         "at 0x%lx, size 0x%x\n", mtd->name,
 124                         mtdblk->cache_offset, mtdblk->cache_size);
 125
 126         ret = erase_write (mtd, mtdblk->cache_offset,
 127                            mtdblk->cache_size, mtdblk->cache_data);
 128         if (ret)
 129                 return ret;
 130
 131         /*
 132          * Here we could arguably set the cache state to STATE_CLEAN.
 133          * However this could lead to inconsistency since we will not
 134          * be notified if this content is altered on the flash by other
 135          * means.  Let's declare it empty and leave buffering tasks to
 136          * the buffer cache instead.
 137          */
 138         mtdblk->cache_state = STATE_EMPTY;
 139         return 0;
 140 }
 141
 142
 143 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 144                             int len, const char *buf)
 145 {
 146         struct mtd_info *mtd = mtdblk->mbd.mtd;
 147         unsigned int sect_size = mtdblk->cache_size;
 148         size_t retlen;
 149         int ret;
 150
 151         pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
 152                 mtd->name, pos, len);
 153
 154         if (!sect_size)
 155                 return mtd->write(mtd, pos, len, &retlen, buf);
 156
 157         while (len > 0) {
 158                 unsigned long sect_start = (pos/sect_size)*sect_size;
 159                 unsigned int offset = pos - sect_start;
 160                 unsigned int size = sect_size - offset;
 161                 if( size > len )
 162                         size = len;
 163
 164                 if (size == sect_size) {
 165                         /*
 166                          * We are covering a whole sector.  Thus there is no
 167                          * need to bother with the cache while it may still be
 168                          * useful for other partial writes.
 169                          */
 170                         ret = erase_write (mtd, pos, size, buf);
 171                         if (ret)
 172                                 return ret;
 173                 } else {
 174                         /* Partial sector: need to use the cache */
 175
 176                         if (mtdblk->cache_state == STATE_DIRTY &&
 177                             mtdblk->cache_offset != sect_start) {
 178                                 ret = write_cached_data(mtdblk);
 179                                 if (ret)
 180                                         return ret;
 181                         }
 182
 183                         if (mtdblk->cache_state == STATE_EMPTY ||
 184                             mtdblk->cache_offset != sect_start) {
 185                                 /* fill the cache with the current sector */
 186                                 mtdblk->cache_state = STATE_EMPTY;
 187                                 ret = mtd->read(mtd, sect_start, sect_size,
 188                                                 &retlen, mtdblk->cache_data);
 189                                 if (ret)
 190                                         return ret;
 191                                 if (retlen != sect_size)
 192                                         return -EIO;
 193
 194                                 mtdblk->cache_offset = sect_start;
 195                                 mtdblk->cache_size = sect_size;
 196                                 mtdblk->cache_state = STATE_CLEAN;
 197                         }
 198
 199                         /* write data to our local cache */
 200                         memcpy (mtdblk->cache_data + offset, buf, size);
 201                         mtdblk->cache_state = STATE_DIRTY;
 202                 }
 203
 204                 buf += size;
 205                 pos += size;
 206                 len -= size;
 207         }
 208
 209         return 0;
 210 }
 211
 212
 213 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 214                            int len, char *buf)
 215 {
 216         struct mtd_info *mtd = mtdblk->mbd.mtd;
 217         unsigned int sect_size = mtdblk->cache_size;
 218         size_t retlen;
 219         int ret;
 220
 221         pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 222                         mtd->name, pos, len);
 223
 224         if (!sect_size)
 225                 return mtd->read(mtd, pos, len, &retlen, buf);
 226
 227         while (len > 0) {
 228                 unsigned long sect_start = (pos/sect_size)*sect_size;
 229                 unsigned int offset = pos - sect_start;
 230                 unsigned int size = sect_size - offset;
 231                 if (size > len)
 232                         size = len;
 233
 234                 /*
 235                  * Check if the requested data is already cached
 236                  * Read the requested amount of data from our internal cache if it
 237                  * contains what we want, otherwise we read the data directly
 238                  * from flash.
 239                  */
 240                 if (mtdblk->cache_state != STATE_EMPTY &&
 241                     mtdblk->cache_offset == sect_start) {
 242                         memcpy (buf, mtdblk->cache_data + offset, size);
 243                 } else {
 244                         ret = mtd->read(mtd, pos, size, &retlen, buf);
 245                         if (ret)
 246                                 return ret;
 247                         if (retlen != size)
 248                                 return -EIO;
 249                 }
 250
 251                 buf += size;
 252                 pos += size;
 253                 len -= size;
 254         }
 255
 256         return 0;
 257 }
 258
 259 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
 260                               unsigned long block, char *buf)
 261 {
 262         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 263         return do_cached_read(mtdblk, block<<9, 512, buf);
 264 }
 265
 266 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
 267                               unsigned long block, char *buf)
 268 {
 269         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 270         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 271                 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
 272                 if (!mtdblk->cache_data)
 273                         return -EINTR;
 274                 /* -EINTR is not really correct, but it is the best match
 275                  * documented in man 2 write for all cases.  We could also
 276                  * return -EAGAIN sometimes, but why bother?
 277                  */
 278         }
 279         return do_cached_write(mtdblk, block<<9, 512, buf);
 280 }
 281
 282 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 283 {
 284         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 285
 286         pr_debug("mtdblock_open\n");
 287
 288         mutex_lock(&mtdblks_lock);
 289         if (mtdblk->count) {
 290                 mtdblk->count++;
 291                 mutex_unlock(&mtdblks_lock);
 292                 return 0;
 293         }
 294
 295         /* OK, it's not open. Create cache info for it */
 296         mtdblk->count = 1;
 297         mutex_init(&mtdblk->cache_mutex);
 298         mtdblk->cache_state = STATE_EMPTY;
 299         if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
 300                 mtdblk->cache_size = mbd->mtd->erasesize;
 301                 mtdblk->cache_data = NULL;
 302         }
 303
 304         mutex_unlock(&mtdblks_lock);
 305
 306         pr_debug("ok\n");
 307
 308         return 0;
 309 }
 310
 311 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 312 {
 313         struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 314
 315         pr_debug("mtdblock_release\n");
 316
 317         mutex_lock(&mtdblks_lock);
 318
 319         mutex_lock(&mtdblk->cache_mutex);
 320         write_cached_data(mtdblk);
 321         mutex_unlock(&mtdblk->cache_mutex);
 322
 323         if (!--mtdblk->count) {
 324                 /* It was the last usage. Free the cache */
 325                 if (mbd->mtd->sync)
 326                         mbd->mtd->sync(mbd->mtd);
 327                 vfree(mtdblk->cache_data);
 328         }
 329
 330         mutex_unlock(&mtdblks_lock);
 331
 332         pr_debug("ok\n");
 333
 334         return 0;
 335 }
 336
 337 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 338 {
 339         struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 340
 341         mutex_lock(&mtdblk->cache_mutex);
 342         write_cached_data(mtdblk);
 343         mutex_unlock(&mtdblk->cache_mutex);
 344
 345         if (dev->mtd->sync)
 346                 dev->mtd->sync(dev->mtd);
 347         return 0;
 348 }
 349
 350 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 351 {
 352         struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 353
 354         if (!dev)
 355                 return;
 356
 357         dev->mbd.mtd = mtd;
 358         dev->mbd.devnum = mtd->index;
 359
 360         dev->mbd.size = mtd->size >> 9;
 361         dev->mbd.tr = tr;
 362
 363         if (!(mtd->flags & MTD_WRITEABLE))
 364                 dev->mbd.readonly = 1;
 365
 366         if (add_mtd_blktrans_dev(&dev->mbd))
 367                 kfree(dev);
 368 }
 369
 370 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 371 {
 372         del_mtd_blktrans_dev(dev);
 373 }
 374
 375 static struct mtd_blktrans_ops mtdblock_tr = {
 376         .name           = "mtdblock",
 377         .major          = 31,
 378         .part_bits      = 0,
 379         .blksize        = 512,
 380         .open           = mtdblock_open,
 381         .flush          = mtdblock_flush,
 382         .release        = mtdblock_release,
 383         .readsect       = mtdblock_readsect,
 384         .writesect      = mtdblock_writesect,
 385         .add_mtd        = mtdblock_add_mtd,
 386         .remove_dev     = mtdblock_remove_dev,
 387         .owner          = THIS_MODULE,
 388 };
 389
 390 static int __init init_mtdblock(void)
 391 {
 392         return register_mtd_blktrans(&mtdblock_tr);
 393 }
 394
 395 static void __exit cleanup_mtdblock(void)
 396 {
 397         deregister_mtd_blktrans(&mtdblock_tr);
 398 }
 399
 400 module_init(init_mtdblock);
 401 module_exit(cleanup_mtdblock);
 402
 403
 404 MODULE_LICENSE("GPL");
 405 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
 406 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");