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