drivers/mtd/mtdconcat.c

   1 /*
   2  * MTD device concatenation layer
   3  *
   4  * (C) 2002 Robert Kaiser <rkaiser@sysgo.de>
   5  *
   6  * NAND support by Christian Gan <cgan@iders.ca>
   7  *
   8  * This code is GPL
   9  *
  10  * $Id: mtdconcat.c,v 1.8 2003/06/30 11:01:26 dwmw2 Exp $
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/types.h>
  15 #include <linux/kernel.h>
  16 #include <linux/slab.h>
  17
  18 #include <linux/mtd/mtd.h>
  19 #include <linux/mtd/concat.h>
  20
  21 /*
  22  * Our storage structure:
  23  * Subdev points to an array of pointers to struct mtd_info objects
  24  * which is allocated along with this structure
  25  *
  26  */
  27 struct mtd_concat {
  28         struct mtd_info mtd;
  29         int num_subdev;
  30         struct mtd_info **subdev;
  31 };
  32
  33 /*
  34  * how to calculate the size required for the above structure,
  35  * including the pointer array subdev points to:
  36  */
  37 #define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)    \
  38         ((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))
  39
  40 /*
  41  * Given a pointer to the MTD object in the mtd_concat structure,
  42  * we can retrieve the pointer to that structure with this macro.
  43  */
  44 #define CONCAT(x)  ((struct mtd_concat *)(x))
  45
  46 /*
  47  * MTD methods which look up the relevant subdevice, translate the
  48  * effective address and pass through to the subdevice.
  49  */
  50
  51 static int
  52 concat_read(struct mtd_info *mtd, loff_t from, size_t len,
  53             size_t * retlen, u_char * buf)
  54 {
  55         struct mtd_concat *concat = CONCAT(mtd);
  56         int err = -EINVAL;
  57         int i;
  58
  59         *retlen = 0;
  60
  61         for (i = 0; i < concat->num_subdev; i++) {
  62                 struct mtd_info *subdev = concat->subdev[i];
  63                 size_t size, retsize;
  64
  65                 if (from >= subdev->size) {
  66                         /* Not destined for this subdev */
  67                         size = 0;
  68                         from -= subdev->size;
  69                         continue;
  70                 }
  71                 if (from + len > subdev->size)
  72                         /* First part goes into this subdev */
  73                         size = subdev->size - from;
  74                 else
  75                         /* Entire transaction goes into this subdev */
  76                         size = len;
  77
  78                 err = subdev->read(subdev, from, size, &retsize, buf);
  79
  80                 if (err)
  81                         break;
  82
  83                 *retlen += retsize;
  84                 len -= size;
  85                 if (len == 0)
  86                         break;
  87
  88                 err = -EINVAL;
  89                 buf += size;
  90                 from = 0;
  91         }
  92         return err;
  93 }
  94
  95 static int
  96 concat_write(struct mtd_info *mtd, loff_t to, size_t len,
  97              size_t * retlen, const u_char * buf)
  98 {
  99         struct mtd_concat *concat = CONCAT(mtd);
 100         int err = -EINVAL;
 101         int i;
 102
 103         if (!(mtd->flags & MTD_WRITEABLE))
 104                 return -EROFS;
 105
 106         *retlen = 0;
 107
 108         for (i = 0; i < concat->num_subdev; i++) {
 109                 struct mtd_info *subdev = concat->subdev[i];
 110                 size_t size, retsize;
 111
 112                 if (to >= subdev->size) {
 113                         size = 0;
 114                         to -= subdev->size;
 115                         continue;
 116                 }
 117                 if (to + len > subdev->size)
 118                         size = subdev->size - to;
 119                 else
 120                         size = len;
 121
 122                 if (!(subdev->flags & MTD_WRITEABLE))
 123                         err = -EROFS;
 124                 else
 125                         err = subdev->write(subdev, to, size, &retsize, buf);
 126
 127                 if (err)
 128                         break;
 129
 130                 *retlen += retsize;
 131                 len -= size;
 132                 if (len == 0)
 133                         break;
 134
 135                 err = -EINVAL;
 136                 buf += size;
 137                 to = 0;
 138         }
 139         return err;
 140 }
 141
 142 static int
 143 concat_read_ecc(struct mtd_info *mtd, loff_t from, size_t len,
 144                 size_t * retlen, u_char * buf, u_char * eccbuf,
 145                 struct nand_oobinfo *oobsel)
 146 {
 147         struct mtd_concat *concat = CONCAT(mtd);
 148         int err = -EINVAL;
 149         int i;
 150
 151         *retlen = 0;
 152
 153         for (i = 0; i < concat->num_subdev; i++) {
 154                 struct mtd_info *subdev = concat->subdev[i];
 155                 size_t size, retsize;
 156
 157                 if (from >= subdev->size) {
 158                         /* Not destined for this subdev */
 159                         size = 0;
 160                         from -= subdev->size;
 161                         continue;
 162                 }
 163
 164                 if (from + len > subdev->size)
 165                         /* First part goes into this subdev */
 166                         size = subdev->size - from;
 167                 else
 168                         /* Entire transaction goes into this subdev */
 169                         size = len;
 170
 171                 if (subdev->read_ecc)
 172                         err = subdev->read_ecc(subdev, from, size,
 173                                                &retsize, buf, eccbuf, oobsel);
 174                 else
 175                         err = -EINVAL;
 176
 177                 if (err)
 178                         break;
 179
 180                 *retlen += retsize;
 181                 len -= size;
 182                 if (len == 0)
 183                         break;
 184
 185                 err = -EINVAL;
 186                 buf += size;
 187                 if (eccbuf) {
 188                         eccbuf += subdev->oobsize;
 189                         /* in nand.c at least, eccbufs are
 190                            tagged with 2 (int)eccstatus'; we
 191                            must account for these */
 192                         eccbuf += 2 * (sizeof (int));
 193                 }
 194                 from = 0;
 195         }
 196         return err;
 197 }
 198
 199 static int
 200 concat_write_ecc(struct mtd_info *mtd, loff_t to, size_t len,
 201                  size_t * retlen, const u_char * buf, u_char * eccbuf,
 202                  struct nand_oobinfo *oobsel)
 203 {
 204         struct mtd_concat *concat = CONCAT(mtd);
 205         int err = -EINVAL;
 206         int i;
 207
 208         if (!(mtd->flags & MTD_WRITEABLE))
 209                 return -EROFS;
 210
 211         *retlen = 0;
 212
 213         for (i = 0; i < concat->num_subdev; i++) {
 214                 struct mtd_info *subdev = concat->subdev[i];
 215                 size_t size, retsize;
 216
 217                 if (to >= subdev->size) {
 218                         size = 0;
 219                         to -= subdev->size;
 220                         continue;
 221                 }
 222                 if (to + len > subdev->size)
 223                         size = subdev->size - to;
 224                 else
 225                         size = len;
 226
 227                 if (!(subdev->flags & MTD_WRITEABLE))
 228                         err = -EROFS;
 229                 else if (subdev->write_ecc)
 230                         err = subdev->write_ecc(subdev, to, size,
 231                                                 &retsize, buf, eccbuf, oobsel);
 232                 else
 233                         err = -EINVAL;
 234
 235                 if (err)
 236                         break;
 237
 238                 *retlen += retsize;
 239                 len -= size;
 240                 if (len == 0)
 241                         break;
 242
 243                 err = -EINVAL;
 244                 buf += size;
 245                 if (eccbuf)
 246                         eccbuf += subdev->oobsize;
 247                 to = 0;
 248         }
 249         return err;
 250 }
 251
 252 static int
 253 concat_read_oob(struct mtd_info *mtd, loff_t from, size_t len,
 254                 size_t * retlen, u_char * buf)
 255 {
 256         struct mtd_concat *concat = CONCAT(mtd);
 257         int err = -EINVAL;
 258         int i;
 259
 260         *retlen = 0;
 261
 262         for (i = 0; i < concat->num_subdev; i++) {
 263                 struct mtd_info *subdev = concat->subdev[i];
 264                 size_t size, retsize;
 265
 266                 if (from >= subdev->size) {
 267                         /* Not destined for this subdev */
 268                         size = 0;
 269                         from -= subdev->size;
 270                         continue;
 271                 }
 272                 if (from + len > subdev->size)
 273                         /* First part goes into this subdev */
 274                         size = subdev->size - from;
 275                 else
 276                         /* Entire transaction goes into this subdev */
 277                         size = len;
 278
 279                 if (subdev->read_oob)
 280                         err = subdev->read_oob(subdev, from, size,
 281                                                &retsize, buf);
 282                 else
 283                         err = -EINVAL;
 284
 285                 if (err)
 286                         break;
 287
 288                 *retlen += retsize;
 289                 len -= size;
 290                 if (len == 0)
 291                         break;
 292
 293                 err = -EINVAL;
 294                 buf += size;
 295                 from = 0;
 296         }
 297         return err;
 298 }
 299
 300 static int
 301 concat_write_oob(struct mtd_info *mtd, loff_t to, size_t len,
 302                  size_t * retlen, const u_char * buf)
 303 {
 304         struct mtd_concat *concat = CONCAT(mtd);
 305         int err = -EINVAL;
 306         int i;
 307
 308         if (!(mtd->flags & MTD_WRITEABLE))
 309                 return -EROFS;
 310
 311         *retlen = 0;
 312
 313         for (i = 0; i < concat->num_subdev; i++) {
 314                 struct mtd_info *subdev = concat->subdev[i];
 315                 size_t size, retsize;
 316
 317                 if (to >= subdev->size) {
 318                         size = 0;
 319                         to -= subdev->size;
 320                         continue;
 321                 }
 322                 if (to + len > subdev->size)
 323                         size = subdev->size - to;
 324                 else
 325                         size = len;
 326
 327                 if (!(subdev->flags & MTD_WRITEABLE))
 328                         err = -EROFS;
 329                 else if (subdev->write_oob)
 330                         err = subdev->write_oob(subdev, to, size, &retsize,
 331                                                 buf);
 332                 else
 333                         err = -EINVAL;
 334
 335                 if (err)
 336                         break;
 337
 338                 *retlen += retsize;
 339                 len -= size;
 340                 if (len == 0)
 341                         break;
 342
 343                 err = -EINVAL;
 344                 buf += size;
 345                 to = 0;
 346         }
 347         return err;
 348 }
 349
 350 static void concat_erase_callback(struct erase_info *instr)
 351 {
 352         wake_up((wait_queue_head_t *) instr->priv);
 353 }
 354
 355 static int concat_dev_erase(struct mtd_info *mtd, struct erase_info *erase)
 356 {
 357         int err;
 358         wait_queue_head_t waitq;
 359         DECLARE_WAITQUEUE(wait, current);
 360
 361         /*
 362          * This code was stol^H^H^H^Hinspired by mtdchar.c
 363          */
 364         init_waitqueue_head(&waitq);
 365
 366         erase->mtd = mtd;
 367         erase->callback = concat_erase_callback;
 368         erase->priv = (unsigned long) &waitq;
 369
 370         /*
 371          * FIXME: Allow INTERRUPTIBLE. Which means
 372          * not having the wait_queue head on the stack.
 373          */
 374         err = mtd->erase(mtd, erase);
 375         if (!err) {
 376                 set_current_state(TASK_UNINTERRUPTIBLE);
 377                 add_wait_queue(&waitq, &wait);
 378                 if (erase->state != MTD_ERASE_DONE
 379                     && erase->state != MTD_ERASE_FAILED)
 380                         schedule();
 381                 remove_wait_queue(&waitq, &wait);
 382                 set_current_state(TASK_RUNNING);
 383
 384                 err = (erase->state == MTD_ERASE_FAILED) ? -EIO : 0;
 385         }
 386         return err;
 387 }
 388
 389 static int concat_erase(struct mtd_info *mtd, struct erase_info *instr)
 390 {
 391         struct mtd_concat *concat = CONCAT(mtd);
 392         struct mtd_info *subdev;
 393         int i, err;
 394         u_int32_t length;
 395         struct erase_info *erase;
 396
 397         if (!(mtd->flags & MTD_WRITEABLE))
 398                 return -EROFS;
 399
 400         if (instr->addr > concat->mtd.size)
 401                 return -EINVAL;
 402
 403         if (instr->len + instr->addr > concat->mtd.size)
 404                 return -EINVAL;
 405
 406         /*
 407          * Check for proper erase block alignment of the to-be-erased area.
 408          * It is easier to do this based on the super device's erase
 409          * region info rather than looking at each particular sub-device
 410          * in turn.
 411          */
 412         if (!concat->mtd.numeraseregions) {
 413                 /* the easy case: device has uniform erase block size */
 414                 if (instr->addr & (concat->mtd.erasesize - 1))
 415                         return -EINVAL;
 416                 if (instr->len & (concat->mtd.erasesize - 1))
 417                         return -EINVAL;
 418         } else {
 419                 /* device has variable erase size */
 420                 struct mtd_erase_region_info *erase_regions =
 421                     concat->mtd.eraseregions;
 422
 423                 /*
 424                  * Find the erase region where the to-be-erased area begins:
 425                  */
 426                 for (i = 0; i < concat->mtd.numeraseregions &&
 427                      instr->addr >= erase_regions[i].offset; i++) ;
 428                 --i;
 429
 430                 /*
 431                  * Now erase_regions[i] is the region in which the
 432                  * to-be-erased area begins. Verify that the starting
 433                  * offset is aligned to this region's erase size:
 434                  */
 435                 if (instr->addr & (erase_regions[i].erasesize - 1))
 436                         return -EINVAL;
 437
 438                 /*
 439                  * now find the erase region where the to-be-erased area ends:
 440                  */
 441                 for (; i < concat->mtd.numeraseregions &&
 442                      (instr->addr + instr->len) >= erase_regions[i].offset;
 443                      ++i) ;
 444                 --i;
 445                 /*
 446                  * check if the ending offset is aligned to this region's erase size
 447                  */
 448                 if ((instr->addr + instr->len) & (erase_regions[i].erasesize -
 449                                                   1))
 450                         return -EINVAL;
 451         }
 452
 453         /* make a local copy of instr to avoid modifying the caller's struct */
 454         erase = kmalloc(sizeof (struct erase_info), GFP_KERNEL);
 455
 456         if (!erase)
 457                 return -ENOMEM;
 458
 459         *erase = *instr;
 460         length = instr->len;
 461
 462         /*
 463          * find the subdevice where the to-be-erased area begins, adjust
 464          * starting offset to be relative to the subdevice start
 465          */
 466         for (i = 0; i < concat->num_subdev; i++) {
 467                 subdev = concat->subdev[i];
 468                 if (subdev->size <= erase->addr)
 469                         erase->addr -= subdev->size;
 470                 else
 471                         break;
 472         }
 473
 474         /* must never happen since size limit has been verified above */
 475         if (i >= concat->num_subdev)
 476                 BUG();
 477
 478         /* now do the erase: */
 479         err = 0;
 480         for (; length > 0; i++) {
 481                 /* loop for all subdevices affected by this request */
 482                 subdev = concat->subdev[i];     /* get current subdevice */
 483
 484                 /* limit length to subdevice's size: */
 485                 if (erase->addr + length > subdev->size)
 486                         erase->len = subdev->size - erase->addr;
 487                 else
 488                         erase->len = length;
 489
 490                 if (!(subdev->flags & MTD_WRITEABLE)) {
 491                         err = -EROFS;
 492                         break;
 493                 }
 494                 length -= erase->len;
 495                 if ((err = concat_dev_erase(subdev, erase))) {
 496                         /* sanity check: should never happen since
 497                          * block alignment has been checked above */
 498                         if (err == -EINVAL)
 499                                 BUG();
 500                         break;
 501                 }
 502                 /*
 503                  * erase->addr specifies the offset of the area to be
 504                  * erased *within the current subdevice*. It can be
 505                  * non-zero only the first time through this loop, i.e.
 506                  * for the first subdevice where blocks need to be erased.
 507                  * All the following erases must begin at the start of the
 508                  * current subdevice, i.e. at offset zero.
 509                  */
 510                 erase->addr = 0;
 511         }
 512         kfree(erase);
 513         if (err)
 514                 return err;
 515
 516         instr->state = MTD_ERASE_DONE;
 517         if (instr->callback)
 518                 instr->callback(instr);
 519         return 0;
 520 }
 521
 522 static int concat_lock(struct mtd_info *mtd, loff_t ofs, size_t len)
 523 {
 524         struct mtd_concat *concat = CONCAT(mtd);
 525         int i, err = -EINVAL;
 526
 527         if ((len + ofs) > mtd->size)
 528                 return -EINVAL;
 529
 530         for (i = 0; i < concat->num_subdev; i++) {
 531                 struct mtd_info *subdev = concat->subdev[i];
 532                 size_t size;
 533
 534                 if (ofs >= subdev->size) {
 535                         size = 0;
 536                         ofs -= subdev->size;
 537                         continue;
 538                 }
 539                 if (ofs + len > subdev->size)
 540                         size = subdev->size - ofs;
 541                 else
 542                         size = len;
 543
 544                 err = subdev->lock(subdev, ofs, size);
 545
 546                 if (err)
 547                         break;
 548
 549                 len -= size;
 550                 if (len == 0)
 551                         break;
 552
 553                 err = -EINVAL;
 554                 ofs = 0;
 555         }
 556
 557         return err;
 558 }
 559
 560 static int concat_unlock(struct mtd_info *mtd, loff_t ofs, size_t len)
 561 {
 562         struct mtd_concat *concat = CONCAT(mtd);
 563         int i, err = 0;
 564
 565         if ((len + ofs) > mtd->size)
 566                 return -EINVAL;
 567
 568         for (i = 0; i < concat->num_subdev; i++) {
 569                 struct mtd_info *subdev = concat->subdev[i];
 570                 size_t size;
 571
 572                 if (ofs >= subdev->size) {
 573                         size = 0;
 574                         ofs -= subdev->size;
 575                         continue;
 576                 }
 577                 if (ofs + len > subdev->size)
 578                         size = subdev->size - ofs;
 579                 else
 580                         size = len;
 581
 582                 err = subdev->unlock(subdev, ofs, size);
 583
 584                 if (err)
 585                         break;
 586
 587                 len -= size;
 588                 if (len == 0)
 589                         break;
 590
 591                 err = -EINVAL;
 592                 ofs = 0;
 593         }
 594
 595         return err;
 596 }
 597
 598 static void concat_sync(struct mtd_info *mtd)
 599 {
 600         struct mtd_concat *concat = CONCAT(mtd);
 601         int i;
 602
 603         for (i = 0; i < concat->num_subdev; i++) {
 604                 struct mtd_info *subdev = concat->subdev[i];
 605                 subdev->sync(subdev);
 606         }
 607 }
 608
 609 static int concat_suspend(struct mtd_info *mtd)
 610 {
 611         struct mtd_concat *concat = CONCAT(mtd);
 612         int i, rc = 0;
 613
 614         for (i = 0; i < concat->num_subdev; i++) {
 615                 struct mtd_info *subdev = concat->subdev[i];
 616                 if ((rc = subdev->suspend(subdev)) < 0)
 617                         return rc;
 618         }
 619         return rc;
 620 }
 621
 622 static void concat_resume(struct mtd_info *mtd)
 623 {
 624         struct mtd_concat *concat = CONCAT(mtd);
 625         int i;
 626
 627         for (i = 0; i < concat->num_subdev; i++) {
 628                 struct mtd_info *subdev = concat->subdev[i];
 629                 subdev->resume(subdev);
 630         }
 631 }
 632
 633 /*
 634  * This function constructs a virtual MTD device by concatenating
 635  * num_devs MTD devices. A pointer to the new device object is
 636  * stored to *new_dev upon success. This function does _not_
 637  * register any devices: this is the caller's responsibility.
 638  */
 639 struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],   /* subdevices to concatenate */
 640                                    int num_devs,        /* number of subdevices      */
 641                                    char *name)
 642 {                               /* name for the new device   */
 643         int i;
 644         size_t size;
 645         struct mtd_concat *concat;
 646         u_int32_t max_erasesize, curr_erasesize;
 647         int num_erase_region;
 648
 649         printk(KERN_NOTICE "Concatenating MTD devices:\n");
 650         for (i = 0; i < num_devs; i++)
 651                 printk(KERN_NOTICE "(%d): \"%s\"\n", i, subdev[i]->name);
 652         printk(KERN_NOTICE "into device \"%s\"\n", name);
 653
 654         /* allocate the device structure */
 655         size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
 656         concat = kmalloc(size, GFP_KERNEL);
 657         if (!concat) {
 658                 printk
 659                     ("memory allocation error while creating concatenated device \"%s\"\n",
 660                      name);
 661                 return NULL;
 662         }
 663         memset(concat, 0, size);
 664         concat->subdev = (struct mtd_info **) (concat + 1);
 665
 666         /*
 667          * Set up the new "super" device's MTD object structure, check for
 668          * incompatibilites between the subdevices.
 669          */
 670         concat->mtd.type = subdev[0]->type;
 671         concat->mtd.flags = subdev[0]->flags;
 672         concat->mtd.size = subdev[0]->size;
 673         concat->mtd.erasesize = subdev[0]->erasesize;
 674         concat->mtd.oobblock = subdev[0]->oobblock;
 675         concat->mtd.oobsize = subdev[0]->oobsize;
 676         concat->mtd.ecctype = subdev[0]->ecctype;
 677         concat->mtd.eccsize = subdev[0]->eccsize;
 678         if (subdev[0]->read_ecc)
 679                 concat->mtd.read_ecc = concat_read_ecc;
 680         if (subdev[0]->write_ecc)
 681                 concat->mtd.write_ecc = concat_write_ecc;
 682         if (subdev[0]->read_oob)
 683                 concat->mtd.read_oob = concat_read_oob;
 684         if (subdev[0]->write_oob)
 685                 concat->mtd.write_oob = concat_write_oob;
 686
 687         concat->subdev[0] = subdev[0];
 688
 689         for (i = 1; i < num_devs; i++) {
 690                 if (concat->mtd.type != subdev[i]->type) {
 691                         kfree(concat);
 692                         printk("Incompatible device type on \"%s\"\n",
 693                                subdev[i]->name);
 694                         return NULL;
 695                 }
 696                 if (concat->mtd.flags != subdev[i]->flags) {
 697                         /*
 698                          * Expect all flags except MTD_WRITEABLE to be
 699                          * equal on all subdevices.
 700                          */
 701                         if ((concat->mtd.flags ^ subdev[i]->
 702                              flags) & ~MTD_WRITEABLE) {
 703                                 kfree(concat);
 704                                 printk("Incompatible device flags on \"%s\"\n",
 705                                        subdev[i]->name);
 706                                 return NULL;
 707                         } else
 708                                 /* if writeable attribute differs,
 709                                    make super device writeable */
 710                                 concat->mtd.flags |=
 711                                     subdev[i]->flags & MTD_WRITEABLE;
 712                 }
 713                 concat->mtd.size += subdev[i]->size;
 714                 if (concat->mtd.oobblock   !=  subdev[i]->oobblock ||
 715                     concat->mtd.oobsize    !=  subdev[i]->oobsize ||
 716                     concat->mtd.ecctype    !=  subdev[i]->ecctype ||
 717                     concat->mtd.eccsize    !=  subdev[i]->eccsize ||
 718                     !concat->mtd.read_ecc  != !subdev[i]->read_ecc ||
 719                     !concat->mtd.write_ecc != !subdev[i]->write_ecc ||
 720                     !concat->mtd.read_oob  != !subdev[i]->read_oob ||
 721                     !concat->mtd.write_oob != !subdev[i]->write_oob) {
 722                         kfree(concat);
 723                         printk("Incompatible OOB or ECC data on \"%s\"\n",
 724                                subdev[i]->name);
 725                         return NULL;
 726                 }
 727                 concat->subdev[i] = subdev[i];
 728
 729         }
 730
 731         concat->num_subdev = num_devs;
 732         concat->mtd.name = name;
 733
 734         /*
 735          * NOTE: for now, we do not provide any readv()/writev() methods
 736          *       because they are messy to implement and they are not
 737          *       used to a great extent anyway.
 738          */
 739         concat->mtd.erase = concat_erase;
 740         concat->mtd.read = concat_read;
 741         concat->mtd.write = concat_write;
 742         concat->mtd.sync = concat_sync;
 743         concat->mtd.lock = concat_lock;
 744         concat->mtd.unlock = concat_unlock;
 745         concat->mtd.suspend = concat_suspend;
 746         concat->mtd.resume = concat_resume;
 747
 748         /*
 749          * Combine the erase block size info of the subdevices:
 750          *
 751          * first, walk the map of the new device and see how
 752          * many changes in erase size we have
 753          */
 754         max_erasesize = curr_erasesize = subdev[0]->erasesize;
 755         num_erase_region = 1;
 756         for (i = 0; i < num_devs; i++) {
 757                 if (subdev[i]->numeraseregions == 0) {
 758                         /* current subdevice has uniform erase size */
 759                         if (subdev[i]->erasesize != curr_erasesize) {
 760                                 /* if it differs from the last subdevice's erase size, count it */
 761                                 ++num_erase_region;
 762                                 curr_erasesize = subdev[i]->erasesize;
 763                                 if (curr_erasesize > max_erasesize)
 764                                         max_erasesize = curr_erasesize;
 765                         }
 766                 } else {
 767                         /* current subdevice has variable erase size */
 768                         int j;
 769                         for (j = 0; j < subdev[i]->numeraseregions; j++) {
 770
 771                                 /* walk the list of erase regions, count any changes */
 772                                 if (subdev[i]->eraseregions[j].erasesize !=
 773                                     curr_erasesize) {
 774                                         ++num_erase_region;
 775                                         curr_erasesize =
 776                                             subdev[i]->eraseregions[j].
 777                                             erasesize;
 778                                         if (curr_erasesize > max_erasesize)
 779                                                 max_erasesize = curr_erasesize;
 780                                 }
 781                         }
 782                 }
 783         }
 784
 785         if (num_erase_region == 1) {
 786                 /*
 787                  * All subdevices have the same uniform erase size.
 788                  * This is easy:
 789                  */
 790                 concat->mtd.erasesize = curr_erasesize;
 791                 concat->mtd.numeraseregions = 0;
 792         } else {
 793                 /*
 794                  * erase block size varies across the subdevices: allocate
 795                  * space to store the data describing the variable erase regions
 796                  */
 797                 struct mtd_erase_region_info *erase_region_p;
 798                 u_int32_t begin, position;
 799
 800                 concat->mtd.erasesize = max_erasesize;
 801                 concat->mtd.numeraseregions = num_erase_region;
 802                 concat->mtd.eraseregions = erase_region_p =
 803                     kmalloc(num_erase_region *
 804                             sizeof (struct mtd_erase_region_info), GFP_KERNEL);
 805                 if (!erase_region_p) {
 806                         kfree(concat);
 807                         printk
 808                             ("memory allocation error while creating erase region list"
 809                              " for device \"%s\"\n", name);
 810                         return NULL;
 811                 }
 812
 813                 /*
 814                  * walk the map of the new device once more and fill in
 815                  * in erase region info:
 816                  */
 817                 curr_erasesize = subdev[0]->erasesize;
 818                 begin = position = 0;
 819                 for (i = 0; i < num_devs; i++) {
 820                         if (subdev[i]->numeraseregions == 0) {
 821                                 /* current subdevice has uniform erase size */
 822                                 if (subdev[i]->erasesize != curr_erasesize) {
 823                                         /*
 824                                          *  fill in an mtd_erase_region_info structure for the area
 825                                          *  we have walked so far:
 826                                          */
 827                                         erase_region_p->offset = begin;
 828                                         erase_region_p->erasesize =
 829                                             curr_erasesize;
 830                                         erase_region_p->numblocks =
 831                                             (position - begin) / curr_erasesize;
 832                                         begin = position;
 833
 834                                         curr_erasesize = subdev[i]->erasesize;
 835                                         ++erase_region_p;
 836                                 }
 837                                 position += subdev[i]->size;
 838                         } else {
 839                                 /* current subdevice has variable erase size */
 840                                 int j;
 841                                 for (j = 0; j < subdev[i]->numeraseregions; j++) {
 842                                         /* walk the list of erase regions, count any changes */
 843                                         if (subdev[i]->eraseregions[j].
 844                                             erasesize != curr_erasesize) {
 845                                                 erase_region_p->offset = begin;
 846                                                 erase_region_p->erasesize =
 847                                                     curr_erasesize;
 848                                                 erase_region_p->numblocks =
 849                                                     (position -
 850                                                      begin) / curr_erasesize;
 851                                                 begin = position;
 852
 853                                                 curr_erasesize =
 854                                                     subdev[i]->eraseregions[j].
 855                                                     erasesize;
 856                                                 ++erase_region_p;
 857                                         }
 858                                         position +=
 859                                             subdev[i]->eraseregions[j].
 860                                             numblocks * curr_erasesize;
 861                                 }
 862                         }
 863                 }
 864                 /* Now write the final entry */
 865                 erase_region_p->offset = begin;
 866                 erase_region_p->erasesize = curr_erasesize;
 867                 erase_region_p->numblocks = (position - begin) / curr_erasesize;
 868         }
 869
 870         return &concat->mtd;
 871 }
 872
 873 /*
 874  * This function destroys an MTD object obtained from concat_mtd_devs()
 875  */
 876
 877 void mtd_concat_destroy(struct mtd_info *mtd)
 878 {
 879         struct mtd_concat *concat = CONCAT(mtd);
 880         if (concat->mtd.numeraseregions)
 881                 kfree(concat->mtd.eraseregions);
 882         kfree(concat);
 883 }
 884
 885 EXPORT_SYMBOL(mtd_concat_create);
 886 EXPORT_SYMBOL(mtd_concat_destroy);
 887
 888 MODULE_LICENSE("GPL");
 889 MODULE_AUTHOR("Robert Kaiser <rkaiser@sysgo.de>");
 890 MODULE_DESCRIPTION("Generic support for concatenating of MTD devices");