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   1 /*
   2  * Direct MTD block device access
   3  *
   4  * $Id: mtdblock.c,v 1.66 2004/11/25 13:52:52 joern Exp $
   5  *
   6  * (C) 2000-2003 Nicolas Pitre <nico@cam.org>
   7  * (C) 1999-2003 David Woodhouse <dwmw2@infradead.org>
   8  */
   9
  10 #include <linux/config.h>
  11 #include <linux/types.h>
  12 #include <linux/module.h>
  13 #include <linux/kernel.h>
  14 #include <linux/fs.h>
  15 #include <linux/init.h>
  16 #include <linux/slab.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/mtd/mtd.h>
  19 #include <linux/mtd/blktrans.h>
  20
  21 static struct mtdblk_dev {
  22         struct mtd_info *mtd;
  23         int count;
  24         struct semaphore cache_sem;
  25         unsigned char *cache_data;
  26         unsigned long cache_offset;
  27         unsigned int cache_size;
  28         enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
  29 } *mtdblks[MAX_MTD_DEVICES];
  30
  31 /*
  32  * Cache stuff...
  33  *
  34  * Since typical flash erasable sectors are much larger than what Linux's
  35  * buffer cache can handle, we must implement read-modify-write on flash
  36  * sectors for each block write requests.  To avoid over-erasing flash sectors
  37  * and to speed things up, we locally cache a whole flash sector while it is
  38  * being written to until a different sector is required.
  39  */
  40
  41 static void erase_callback(struct erase_info *done)
  42 {
  43         wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
  44         wake_up(wait_q);
  45 }
  46
  47 static int erase_write (struct mtd_info *mtd, unsigned long pos,
  48                         int len, const char *buf)
  49 {
  50         struct erase_info erase;
  51         DECLARE_WAITQUEUE(wait, current);
  52         wait_queue_head_t wait_q;
  53         size_t retlen;
  54         int ret;
  55
  56         /*
  57          * First, let's erase the flash block.
  58          */
  59
  60         init_waitqueue_head(&wait_q);
  61         erase.mtd = mtd;
  62         erase.callback = erase_callback;
  63         erase.addr = pos;
  64         erase.len = len;
  65         erase.priv = (u_long)&wait_q;
  66
  67         set_current_state(TASK_INTERRUPTIBLE);
  68         add_wait_queue(&wait_q, &wait);
  69
  70         ret = MTD_ERASE(mtd, &erase);
  71         if (ret) {
  72                 set_current_state(TASK_RUNNING);
  73                 remove_wait_queue(&wait_q, &wait);
  74                 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
  75                                      "on \"%s\" failed\n",
  76                         pos, len, mtd->name);
  77                 return ret;
  78         }
  79
  80         schedule();  /* Wait for erase to finish. */
  81         remove_wait_queue(&wait_q, &wait);
  82
  83         /*
  84          * Next, writhe data to flash.
  85          */
  86
  87         ret = MTD_WRITE (mtd, pos, len, &retlen, buf);
  88         if (ret)
  89                 return ret;
  90         if (retlen != len)
  91                 return -EIO;
  92         return 0;
  93 }
  94
  95
  96 static int write_cached_data (struct mtdblk_dev *mtdblk)
  97 {
  98         struct mtd_info *mtd = mtdblk->mtd;
  99         int ret;
 100
 101         if (mtdblk->cache_state != STATE_DIRTY)
 102                 return 0;
 103
 104         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" "
 105                         "at 0x%lx, size 0x%x\n", mtd->name,
 106                         mtdblk->cache_offset, mtdblk->cache_size);
 107
 108         ret = erase_write (mtd, mtdblk->cache_offset,
 109                            mtdblk->cache_size, mtdblk->cache_data);
 110         if (ret)
 111                 return ret;
 112
 113         /*
 114          * Here we could argubly set the cache state to STATE_CLEAN.
 115          * However this could lead to inconsistency since we will not
 116          * be notified if this content is altered on the flash by other
 117          * means.  Let's declare it empty and leave buffering tasks to
 118          * the buffer cache instead.
 119          */
 120         mtdblk->cache_state = STATE_EMPTY;
 121         return 0;
 122 }
 123
 124
 125 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 126                             int len, const char *buf)
 127 {
 128         struct mtd_info *mtd = mtdblk->mtd;
 129         unsigned int sect_size = mtdblk->cache_size;
 130         size_t retlen;
 131         int ret;
 132
 133         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
 134                 mtd->name, pos, len);
 135
 136         if (!sect_size)
 137                 return MTD_WRITE (mtd, pos, len, &retlen, buf);
 138
 139         while (len > 0) {
 140                 unsigned long sect_start = (pos/sect_size)*sect_size;
 141                 unsigned int offset = pos - sect_start;
 142                 unsigned int size = sect_size - offset;
 143                 if( size > len )
 144                         size = len;
 145
 146                 if (size == sect_size) {
 147                         /*
 148                          * We are covering a whole sector.  Thus there is no
 149                          * need to bother with the cache while it may still be
 150                          * useful for other partial writes.
 151                          */
 152                         ret = erase_write (mtd, pos, size, buf);
 153                         if (ret)
 154                                 return ret;
 155                 } else {
 156                         /* Partial sector: need to use the cache */
 157
 158                         if (mtdblk->cache_state == STATE_DIRTY &&
 159                             mtdblk->cache_offset != sect_start) {
 160                                 ret = write_cached_data(mtdblk);
 161                                 if (ret)
 162                                         return ret;
 163                         }
 164
 165                         if (mtdblk->cache_state == STATE_EMPTY ||
 166                             mtdblk->cache_offset != sect_start) {
 167                                 /* fill the cache with the current sector */
 168                                 mtdblk->cache_state = STATE_EMPTY;
 169                                 ret = MTD_READ(mtd, sect_start, sect_size, &retlen, mtdblk->cache_data);
 170                                 if (ret)
 171                                         return ret;
 172                                 if (retlen != sect_size)
 173                                         return -EIO;
 174
 175                                 mtdblk->cache_offset = sect_start;
 176                                 mtdblk->cache_size = sect_size;
 177                                 mtdblk->cache_state = STATE_CLEAN;
 178                         }
 179
 180                         /* write data to our local cache */
 181                         memcpy (mtdblk->cache_data + offset, buf, size);
 182                         mtdblk->cache_state = STATE_DIRTY;
 183                 }
 184
 185                 buf += size;
 186                 pos += size;
 187                 len -= size;
 188         }
 189
 190         return 0;
 191 }
 192
 193
 194 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 195                            int len, char *buf)
 196 {
 197         struct mtd_info *mtd = mtdblk->mtd;
 198         unsigned int sect_size = mtdblk->cache_size;
 199         size_t retlen;
 200         int ret;
 201
 202         DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 203                         mtd->name, pos, len);
 204
 205         if (!sect_size)
 206                 return MTD_READ (mtd, pos, len, &retlen, buf);
 207
 208         while (len > 0) {
 209                 unsigned long sect_start = (pos/sect_size)*sect_size;
 210                 unsigned int offset = pos - sect_start;
 211                 unsigned int size = sect_size - offset;
 212                 if (size > len)
 213                         size = len;
 214
 215                 /*
 216                  * Check if the requested data is already cached
 217                  * Read the requested amount of data from our internal cache if it
 218                  * contains what we want, otherwise we read the data directly
 219                  * from flash.
 220                  */
 221                 if (mtdblk->cache_state != STATE_EMPTY &&
 222                     mtdblk->cache_offset == sect_start) {
 223                         memcpy (buf, mtdblk->cache_data + offset, size);
 224                 } else {
 225                         ret = MTD_READ (mtd, pos, size, &retlen, buf);
 226                         if (ret)
 227                                 return ret;
 228                         if (retlen != size)
 229                                 return -EIO;
 230                 }
 231
 232                 buf += size;
 233                 pos += size;
 234                 len -= size;
 235         }
 236
 237         return 0;
 238 }
 239
 240 static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
 241                               unsigned long block, char *buf)
 242 {
 243         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 244         return do_cached_read(mtdblk, block<<9, 512, buf);
 245 }
 246
 247 static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
 248                               unsigned long block, char *buf)
 249 {
 250         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 251         if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 252                 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize);
 253                 if (!mtdblk->cache_data)
 254                         return -EINTR;
 255                 /* -EINTR is not really correct, but it is the best match
 256                  * documented in man 2 write for all cases.  We could also
 257                  * return -EAGAIN sometimes, but why bother?
 258                  */
 259         }
 260         return do_cached_write(mtdblk, block<<9, 512, buf);
 261 }
 262
 263 static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 264 {
 265         struct mtdblk_dev *mtdblk;
 266         struct mtd_info *mtd = mbd->mtd;
 267         int dev = mbd->devnum;
 268
 269         DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n");
 270
 271         if (mtdblks[dev]) {
 272                 mtdblks[dev]->count++;
 273                 return 0;
 274         }
 275
 276         /* OK, it's not open. Create cache info for it */
 277         mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL);
 278         if (!mtdblk)
 279                 return -ENOMEM;
 280
 281         memset(mtdblk, 0, sizeof(*mtdblk));
 282         mtdblk->count = 1;
 283         mtdblk->mtd = mtd;
 284
 285         init_MUTEX (&mtdblk->cache_sem);
 286         mtdblk->cache_state = STATE_EMPTY;
 287         if ((mtdblk->mtd->flags & MTD_CAP_RAM) != MTD_CAP_RAM &&
 288             mtdblk->mtd->erasesize) {
 289                 mtdblk->cache_size = mtdblk->mtd->erasesize;
 290                 mtdblk->cache_data = NULL;
 291         }
 292
 293         mtdblks[dev] = mtdblk;
 294
 295         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 296
 297         return 0;
 298 }
 299
 300 static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 301 {
 302         int dev = mbd->devnum;
 303         struct mtdblk_dev *mtdblk = mtdblks[dev];
 304
 305         DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n");
 306
 307         down(&mtdblk->cache_sem);
 308         write_cached_data(mtdblk);
 309         up(&mtdblk->cache_sem);
 310
 311         if (!--mtdblk->count) {
 312                 /* It was the last usage. Free the device */
 313                 mtdblks[dev] = NULL;
 314                 if (mtdblk->mtd->sync)
 315                         mtdblk->mtd->sync(mtdblk->mtd);
 316                 vfree(mtdblk->cache_data);
 317                 kfree(mtdblk);
 318         }
 319         DEBUG(MTD_DEBUG_LEVEL1, "ok\n");
 320
 321         return 0;
 322 }
 323
 324 static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 325 {
 326         struct mtdblk_dev *mtdblk = mtdblks[dev->devnum];
 327
 328         down(&mtdblk->cache_sem);
 329         write_cached_data(mtdblk);
 330         up(&mtdblk->cache_sem);
 331
 332         if (mtdblk->mtd->sync)
 333                 mtdblk->mtd->sync(mtdblk->mtd);
 334         return 0;
 335 }
 336
 337 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 338 {
 339         struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL);
 340
 341         if (!dev)
 342                 return;
 343
 344         memset(dev, 0, sizeof(*dev));
 345
 346         dev->mtd = mtd;
 347         dev->devnum = mtd->index;
 348         dev->blksize = 512;
 349         dev->size = mtd->size >> 9;
 350         dev->tr = tr;
 351
 352         if (!(mtd->flags & MTD_WRITEABLE))
 353                 dev->readonly = 1;
 354
 355         add_mtd_blktrans_dev(dev);
 356 }
 357
 358 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 359 {
 360         del_mtd_blktrans_dev(dev);
 361         kfree(dev);
 362 }
 363
 364 static struct mtd_blktrans_ops mtdblock_tr = {
 365         .name           = "mtdblock",
 366         .major          = 31,
 367         .part_bits      = 0,
 368         .open           = mtdblock_open,
 369         .flush          = mtdblock_flush,
 370         .release        = mtdblock_release,
 371         .readsect       = mtdblock_readsect,
 372         .writesect      = mtdblock_writesect,
 373         .add_mtd        = mtdblock_add_mtd,
 374         .remove_dev     = mtdblock_remove_dev,
 375         .owner          = THIS_MODULE,
 376 };
 377
 378 static int __init init_mtdblock(void)
 379 {
 380         return register_mtd_blktrans(&mtdblock_tr);
 381 }
 382
 383 static void __exit cleanup_mtdblock(void)
 384 {
 385         deregister_mtd_blktrans(&mtdblock_tr);
 386 }
 387
 388 module_init(init_mtdblock);
 389 module_exit(cleanup_mtdblock);
 390
 391
 392 MODULE_LICENSE("GPL");
 393 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al.");
 394 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");