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