drivers/mtd/devices/block2mtd.c

   1 /*
   2  * block2mtd.c - create an mtd from a block device
   3  *
   4  * Copyright (C) 2001,2002      Simon Evans <spse@secret.org.uk>
   5  * Copyright (C) 2004-2006      Joern Engel <joern@wh.fh-wedel.de>
   6  *
   7  * Licence: GPL
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 /*
  13  * When the first attempt at device initialization fails, we may need to
  14  * wait a little bit and retry. This timeout, by default 3 seconds, gives
  15  * device time to start up. Required on BCM2708 and a few other chipsets.
  16  */
  17 #define MTD_DEFAULT_TIMEOUT     3
  18
  19 #include <linux/module.h>
  20 #include <linux/delay.h>
  21 #include <linux/fs.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/backing-dev.h>
  24 #include <linux/bio.h>
  25 #include <linux/pagemap.h>
  26 #include <linux/list.h>
  27 #include <linux/init.h>
  28 #include <linux/mtd/mtd.h>
  29 #include <linux/mutex.h>
  30 #include <linux/mount.h>
  31 #include <linux/slab.h>
  32 #include <linux/major.h>
  33
  34 /* Info for the block device */
  35 struct block2mtd_dev {
  36         struct list_head list;
  37         struct block_device *blkdev;
  38         struct mtd_info mtd;
  39         struct mutex write_mutex;
  40 };
  41
  42
  43 /* Static info about the MTD, used in cleanup_module */
  44 static LIST_HEAD(blkmtd_device_list);
  45
  46
  47 static struct page *page_read(struct address_space *mapping, int index)
  48 {
  49         return read_mapping_page(mapping, index, NULL);
  50 }
  51
  52 /* erase a specified part of the device */
  53 static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
  54 {
  55         struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
  56         struct page *page;
  57         int index = to >> PAGE_SHIFT;   // page index
  58         int pages = len >> PAGE_SHIFT;
  59         u_long *p;
  60         u_long *max;
  61
  62         while (pages) {
  63                 page = page_read(mapping, index);
  64                 if (IS_ERR(page))
  65                         return PTR_ERR(page);
  66
  67                 max = page_address(page) + PAGE_SIZE;
  68                 for (p=page_address(page); p<max; p++)
  69                         if (*p != -1UL) {
  70                                 lock_page(page);
  71                                 memset(page_address(page), 0xff, PAGE_SIZE);
  72                                 set_page_dirty(page);
  73                                 unlock_page(page);
  74                                 balance_dirty_pages_ratelimited(mapping);
  75                                 break;
  76                         }
  77
  78                 put_page(page);
  79                 pages--;
  80                 index++;
  81         }
  82         return 0;
  83 }
  84 static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
  85 {
  86         struct block2mtd_dev *dev = mtd->priv;
  87         size_t from = instr->addr;
  88         size_t len = instr->len;
  89         int err;
  90
  91         mutex_lock(&dev->write_mutex);
  92         err = _block2mtd_erase(dev, from, len);
  93         mutex_unlock(&dev->write_mutex);
  94         if (err)
  95                 pr_err("erase failed err = %d\n", err);
  96
  97         return err;
  98 }
  99
 100
 101 static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
 102                 size_t *retlen, u_char *buf)
 103 {
 104         struct block2mtd_dev *dev = mtd->priv;
 105         struct page *page;
 106         int index = from >> PAGE_SHIFT;
 107         int offset = from & (PAGE_SIZE-1);
 108         int cpylen;
 109
 110         while (len) {
 111                 if ((offset + len) > PAGE_SIZE)
 112                         cpylen = PAGE_SIZE - offset;    // multiple pages
 113                 else
 114                         cpylen = len;   // this page
 115                 len = len - cpylen;
 116
 117                 page = page_read(dev->blkdev->bd_inode->i_mapping, index);
 118                 if (IS_ERR(page))
 119                         return PTR_ERR(page);
 120
 121                 memcpy(buf, page_address(page) + offset, cpylen);
 122                 put_page(page);
 123
 124                 if (retlen)
 125                         *retlen += cpylen;
 126                 buf += cpylen;
 127                 offset = 0;
 128                 index++;
 129         }
 130         return 0;
 131 }
 132
 133
 134 /* write data to the underlying device */
 135 static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
 136                 loff_t to, size_t len, size_t *retlen)
 137 {
 138         struct page *page;
 139         struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
 140         int index = to >> PAGE_SHIFT;   // page index
 141         int offset = to & ~PAGE_MASK;   // page offset
 142         int cpylen;
 143
 144         while (len) {
 145                 if ((offset+len) > PAGE_SIZE)
 146                         cpylen = PAGE_SIZE - offset;    // multiple pages
 147                 else
 148                         cpylen = len;                   // this page
 149                 len = len - cpylen;
 150
 151                 page = page_read(mapping, index);
 152                 if (IS_ERR(page))
 153                         return PTR_ERR(page);
 154
 155                 if (memcmp(page_address(page)+offset, buf, cpylen)) {
 156                         lock_page(page);
 157                         memcpy(page_address(page) + offset, buf, cpylen);
 158                         set_page_dirty(page);
 159                         unlock_page(page);
 160                         balance_dirty_pages_ratelimited(mapping);
 161                 }
 162                 put_page(page);
 163
 164                 if (retlen)
 165                         *retlen += cpylen;
 166
 167                 buf += cpylen;
 168                 offset = 0;
 169                 index++;
 170         }
 171         return 0;
 172 }
 173
 174
 175 static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
 176                 size_t *retlen, const u_char *buf)
 177 {
 178         struct block2mtd_dev *dev = mtd->priv;
 179         int err;
 180
 181         mutex_lock(&dev->write_mutex);
 182         err = _block2mtd_write(dev, buf, to, len, retlen);
 183         mutex_unlock(&dev->write_mutex);
 184         if (err > 0)
 185                 err = 0;
 186         return err;
 187 }
 188
 189
 190 /* sync the device - wait until the write queue is empty */
 191 static void block2mtd_sync(struct mtd_info *mtd)
 192 {
 193         struct block2mtd_dev *dev = mtd->priv;
 194         sync_blockdev(dev->blkdev);
 195         return;
 196 }
 197
 198
 199 static void block2mtd_free_device(struct block2mtd_dev *dev)
 200 {
 201         if (!dev)
 202                 return;
 203
 204         kfree(dev->mtd.name);
 205
 206         if (dev->blkdev) {
 207                 invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
 208                                         0, -1);
 209                 blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 210         }
 211
 212         kfree(dev);
 213 }
 214
 215
 216 static struct block2mtd_dev *add_device(char *devname, int erase_size,
 217                 int timeout)
 218 {
 219 #ifndef MODULE
 220         int i;
 221 #endif
 222         const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
 223         struct block_device *bdev;
 224         struct block2mtd_dev *dev;
 225         char *name;
 226
 227         if (!devname)
 228                 return NULL;
 229
 230         dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
 231         if (!dev)
 232                 return NULL;
 233
 234         /* Get a handle on the device */
 235         bdev = blkdev_get_by_path(devname, mode, dev);
 236
 237 #ifndef MODULE
 238         /*
 239          * We might not have the root device mounted at this point.
 240          * Try to resolve the device name by other means.
 241          */
 242         for (i = 0; IS_ERR(bdev) && i <= timeout; i++) {
 243                 dev_t devt;
 244
 245                 if (i)
 246                         /*
 247                          * Calling wait_for_device_probe in the first loop
 248                          * was not enough, sleep for a bit in subsequent
 249                          * go-arounds.
 250                          */
 251                         msleep(1000);
 252                 wait_for_device_probe();
 253
 254                 devt = name_to_dev_t(devname);
 255                 if (!devt)
 256                         continue;
 257                 bdev = blkdev_get_by_dev(devt, mode, dev);
 258         }
 259 #endif
 260
 261         if (IS_ERR(bdev)) {
 262                 pr_err("error: cannot open device %s\n", devname);
 263                 goto err_free_block2mtd;
 264         }
 265         dev->blkdev = bdev;
 266
 267         if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
 268                 pr_err("attempting to use an MTD device as a block device\n");
 269                 goto err_free_block2mtd;
 270         }
 271
 272         if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
 273                 pr_err("erasesize must be a divisor of device size\n");
 274                 goto err_free_block2mtd;
 275         }
 276
 277         mutex_init(&dev->write_mutex);
 278
 279         /* Setup the MTD structure */
 280         /* make the name contain the block device in */
 281         name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
 282         if (!name)
 283                 goto err_destroy_mutex;
 284
 285         dev->mtd.name = name;
 286
 287         dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
 288         dev->mtd.erasesize = erase_size;
 289         dev->mtd.writesize = 1;
 290         dev->mtd.writebufsize = PAGE_SIZE;
 291         dev->mtd.type = MTD_RAM;
 292         dev->mtd.flags = MTD_CAP_RAM;
 293         dev->mtd._erase = block2mtd_erase;
 294         dev->mtd._write = block2mtd_write;
 295         dev->mtd._sync = block2mtd_sync;
 296         dev->mtd._read = block2mtd_read;
 297         dev->mtd.priv = dev;
 298         dev->mtd.owner = THIS_MODULE;
 299
 300         if (mtd_device_register(&dev->mtd, NULL, 0)) {
 301                 /* Device didn't get added, so free the entry */
 302                 goto err_destroy_mutex;
 303         }
 304
 305         list_add(&dev->list, &blkmtd_device_list);
 306         pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 307                 dev->mtd.index,
 308                 dev->mtd.name + strlen("block2mtd: "),
 309                 dev->mtd.erasesize >> 10, dev->mtd.erasesize);
 310         return dev;
 311
 312 err_destroy_mutex:
 313         mutex_destroy(&dev->write_mutex);
 314 err_free_block2mtd:
 315         block2mtd_free_device(dev);
 316         return NULL;
 317 }
 318
 319
 320 /* This function works similar to reguler strtoul.  In addition, it
 321  * allows some suffixes for a more human-readable number format:
 322  * ki, Ki, kiB, KiB     - multiply result with 1024
 323  * Mi, MiB              - multiply result with 1024^2
 324  * Gi, GiB              - multiply result with 1024^3
 325  */
 326 static int ustrtoul(const char *cp, char **endp, unsigned int base)
 327 {
 328         unsigned long result = simple_strtoul(cp, endp, base);
 329         switch (**endp) {
 330         case 'G' :
 331                 result *= 1024;
 332         case 'M':
 333                 result *= 1024;
 334         case 'K':
 335         case 'k':
 336                 result *= 1024;
 337         /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
 338                 if ((*endp)[1] == 'i') {
 339                         if ((*endp)[2] == 'B')
 340                                 (*endp) += 3;
 341                         else
 342                                 (*endp) += 2;
 343                 }
 344         }
 345         return result;
 346 }
 347
 348
 349 static int parse_num(size_t *num, const char *token)
 350 {
 351         char *endp;
 352         size_t n;
 353
 354         n = (size_t) ustrtoul(token, &endp, 0);
 355         if (*endp)
 356                 return -EINVAL;
 357
 358         *num = n;
 359         return 0;
 360 }
 361
 362
 363 static inline void kill_final_newline(char *str)
 364 {
 365         char *newline = strrchr(str, '\n');
 366         if (newline && !newline[1])
 367                 *newline = 0;
 368 }
 369
 370
 371 #ifndef MODULE
 372 static int block2mtd_init_called = 0;
 373 /* 80 for device, 12 for erase size */
 374 static char block2mtd_paramline[80 + 12];
 375 #endif
 376
 377 static int block2mtd_setup2(const char *val)
 378 {
 379         /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
 380         char buf[80 + 12 + 80 + 8];
 381         char *str = buf;
 382         char *token[2];
 383         char *name;
 384         size_t erase_size = PAGE_SIZE;
 385         unsigned long timeout = MTD_DEFAULT_TIMEOUT;
 386         int i, ret;
 387
 388         if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {
 389                 pr_err("parameter too long\n");
 390                 return 0;
 391         }
 392
 393         strcpy(str, val);
 394         kill_final_newline(str);
 395
 396         for (i = 0; i < 2; i++)
 397                 token[i] = strsep(&str, ",");
 398
 399         if (str) {
 400                 pr_err("too many arguments\n");
 401                 return 0;
 402         }
 403
 404         if (!token[0]) {
 405                 pr_err("no argument\n");
 406                 return 0;
 407         }
 408
 409         name = token[0];
 410         if (strlen(name) + 1 > 80) {
 411                 pr_err("device name too long\n");
 412                 return 0;
 413         }
 414
 415         if (token[1]) {
 416                 ret = parse_num(&erase_size, token[1]);
 417                 if (ret) {
 418                         pr_err("illegal erase size\n");
 419                         return 0;
 420                 }
 421         }
 422
 423         add_device(name, erase_size, timeout);
 424
 425         return 0;
 426 }
 427
 428
 429 static int block2mtd_setup(const char *val, const struct kernel_param *kp)
 430 {
 431 #ifdef MODULE
 432         return block2mtd_setup2(val);
 433 #else
 434         /* If more parameters are later passed in via
 435            /sys/module/block2mtd/parameters/block2mtd
 436            and block2mtd_init() has already been called,
 437            we can parse the argument now. */
 438
 439         if (block2mtd_init_called)
 440                 return block2mtd_setup2(val);
 441
 442         /* During early boot stage, we only save the parameters
 443            here. We must parse them later: if the param passed
 444            from kernel boot command line, block2mtd_setup() is
 445            called so early that it is not possible to resolve
 446            the device (even kmalloc() fails). Deter that work to
 447            block2mtd_setup2(). */
 448
 449         strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
 450
 451         return 0;
 452 #endif
 453 }
 454
 455
 456 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
 457 MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
 458
 459 static int __init block2mtd_init(void)
 460 {
 461         int ret = 0;
 462
 463 #ifndef MODULE
 464         if (strlen(block2mtd_paramline))
 465                 ret = block2mtd_setup2(block2mtd_paramline);
 466         block2mtd_init_called = 1;
 467 #endif
 468
 469         return ret;
 470 }
 471
 472
 473 static void block2mtd_exit(void)
 474 {
 475         struct list_head *pos, *next;
 476
 477         /* Remove the MTD devices */
 478         list_for_each_safe(pos, next, &blkmtd_device_list) {
 479                 struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
 480                 block2mtd_sync(&dev->mtd);
 481                 mtd_device_unregister(&dev->mtd);
 482                 mutex_destroy(&dev->write_mutex);
 483                 pr_info("mtd%d: [%s] removed\n",
 484                         dev->mtd.index,
 485                         dev->mtd.name + strlen("block2mtd: "));
 486                 list_del(&dev->list);
 487                 block2mtd_free_device(dev);
 488         }
 489 }
 490
 491 late_initcall(block2mtd_init);
 492 module_exit(block2mtd_exit);
 493
 494 MODULE_LICENSE("GPL");
 495 MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
 496 MODULE_DESCRIPTION("Emulate an MTD using a block device");