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
  11 #include <linux/mtd/mtd.h>
  12 #include <linux/compat.h>
  13 #include <linux/mtd/concat.h>
  14 #include <ubi_uboot.h>
  15
  16 /*
  17  * Our storage structure:
  18  * Subdev points to an array of pointers to struct mtd_info objects
  19  * which is allocated along with this structure
  20  *
  21  */
  22 struct mtd_concat {
  23         struct mtd_info mtd;
  24         int num_subdev;
  25         struct mtd_info **subdev;
  26 };
  27
  28 /*
  29  * how to calculate the size required for the above structure,
  30  * including the pointer array subdev points to:
  31  */
  32 #define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)    \
  33         ((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))
  34
  35 /*
  36  * Given a pointer to the MTD object in the mtd_concat structure,
  37  * we can retrieve the pointer to that structure with this macro.
  38  */
  39 #define CONCAT(x)  ((struct mtd_concat *)(x))
  40
  41 /*
  42  * MTD methods which look up the relevant subdevice, translate the
  43  * effective address and pass through to the subdevice.
  44  */
  45
  46 static int
  47 concat_read(struct mtd_info *mtd, loff_t from, size_t len,
  48             size_t * retlen, u_char * buf)
  49 {
  50         struct mtd_concat *concat = CONCAT(mtd);
  51         int ret = 0, err;
  52         int i;
  53
  54         *retlen = 0;
  55
  56         for (i = 0; i < concat->num_subdev; i++) {
  57                 struct mtd_info *subdev = concat->subdev[i];
  58                 size_t size, retsize;
  59
  60                 if (from >= subdev->size) {
  61                         /* Not destined for this subdev */
  62                         size = 0;
  63                         from -= subdev->size;
  64                         continue;
  65                 }
  66                 if (from + len > subdev->size)
  67                         /* First part goes into this subdev */
  68                         size = subdev->size - from;
  69                 else
  70                         /* Entire transaction goes into this subdev */
  71                         size = len;
  72
  73                 err = mtd_read(subdev, from, size, &retsize, buf);
  74
  75                 /* Save information about bitflips! */
  76                 if (unlikely(err)) {
  77                         if (mtd_is_eccerr(err)) {
  78                                 mtd->ecc_stats.failed++;
  79                                 ret = err;
  80                         } else if (mtd_is_bitflip(err)) {
  81                                 mtd->ecc_stats.corrected++;
  82                                 /* Do not overwrite -EBADMSG !! */
  83                                 if (!ret)
  84                                         ret = err;
  85                         } else
  86                                 return err;
  87                 }
  88
  89                 *retlen += retsize;
  90                 len -= size;
  91                 if (len == 0)
  92                         return ret;
  93
  94                 buf += size;
  95                 from = 0;
  96         }
  97         return -EINVAL;
  98 }
  99
 100 static int
 101 concat_write(struct mtd_info *mtd, loff_t to, size_t len,
 102              size_t * retlen, const u_char * buf)
 103 {
 104         struct mtd_concat *concat = CONCAT(mtd);
 105         int err = -EINVAL;
 106         int i;
 107
 108         *retlen = 0;
 109
 110         for (i = 0; i < concat->num_subdev; i++) {
 111                 struct mtd_info *subdev = concat->subdev[i];
 112                 size_t size, retsize;
 113
 114                 if (to >= subdev->size) {
 115                         size = 0;
 116                         to -= subdev->size;
 117                         continue;
 118                 }
 119                 if (to + len > subdev->size)
 120                         size = subdev->size - to;
 121                 else
 122                         size = len;
 123
 124                 err = mtd_write(subdev, to, size, &retsize, buf);
 125                 if (err)
 126                         break;
 127
 128                 *retlen += retsize;
 129                 len -= size;
 130                 if (len == 0)
 131                         break;
 132
 133                 err = -EINVAL;
 134                 buf += size;
 135                 to = 0;
 136         }
 137         return err;
 138 }
 139
 140 static int
 141 concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
 142 {
 143         struct mtd_concat *concat = CONCAT(mtd);
 144         struct mtd_oob_ops devops = *ops;
 145         int i, err, ret = 0;
 146
 147         ops->retlen = ops->oobretlen = 0;
 148
 149         for (i = 0; i < concat->num_subdev; i++) {
 150                 struct mtd_info *subdev = concat->subdev[i];
 151
 152                 if (from >= subdev->size) {
 153                         from -= subdev->size;
 154                         continue;
 155                 }
 156
 157                 /* partial read ? */
 158                 if (from + devops.len > subdev->size)
 159                         devops.len = subdev->size - from;
 160
 161                 err = mtd_read_oob(subdev, from, &devops);
 162                 ops->retlen += devops.retlen;
 163                 ops->oobretlen += devops.oobretlen;
 164
 165                 /* Save information about bitflips! */
 166                 if (unlikely(err)) {
 167                         if (mtd_is_eccerr(err)) {
 168                                 mtd->ecc_stats.failed++;
 169                                 ret = err;
 170                         } else if (mtd_is_bitflip(err)) {
 171                                 mtd->ecc_stats.corrected++;
 172                                 /* Do not overwrite -EBADMSG !! */
 173                                 if (!ret)
 174                                         ret = err;
 175                         } else
 176                                 return err;
 177                 }
 178
 179                 if (devops.datbuf) {
 180                         devops.len = ops->len - ops->retlen;
 181                         if (!devops.len)
 182                                 return ret;
 183                         devops.datbuf += devops.retlen;
 184                 }
 185                 if (devops.oobbuf) {
 186                         devops.ooblen = ops->ooblen - ops->oobretlen;
 187                         if (!devops.ooblen)
 188                                 return ret;
 189                         devops.oobbuf += ops->oobretlen;
 190                 }
 191
 192                 from = 0;
 193         }
 194         return -EINVAL;
 195 }
 196
 197 static int
 198 concat_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops)
 199 {
 200         struct mtd_concat *concat = CONCAT(mtd);
 201         struct mtd_oob_ops devops = *ops;
 202         int i, err;
 203
 204         if (!(mtd->flags & MTD_WRITEABLE))
 205                 return -EROFS;
 206
 207         ops->retlen = 0;
 208
 209         for (i = 0; i < concat->num_subdev; i++) {
 210                 struct mtd_info *subdev = concat->subdev[i];
 211
 212                 if (to >= subdev->size) {
 213                         to -= subdev->size;
 214                         continue;
 215                 }
 216
 217                 /* partial write ? */
 218                 if (to + devops.len > subdev->size)
 219                         devops.len = subdev->size - to;
 220
 221                 err = mtd_write_oob(subdev, to, &devops);
 222                 ops->retlen += devops.retlen;
 223                 if (err)
 224                         return err;
 225
 226                 if (devops.datbuf) {
 227                         devops.len = ops->len - ops->retlen;
 228                         if (!devops.len)
 229                                 return 0;
 230                         devops.datbuf += devops.retlen;
 231                 }
 232                 if (devops.oobbuf) {
 233                         devops.ooblen = ops->ooblen - ops->oobretlen;
 234                         if (!devops.ooblen)
 235                                 return 0;
 236                         devops.oobbuf += devops.oobretlen;
 237                 }
 238                 to = 0;
 239         }
 240         return -EINVAL;
 241 }
 242
 243 static void concat_erase_callback(struct erase_info *instr)
 244 {
 245         /* Nothing to do here in U-Boot */
 246 }
 247
 248 static int concat_dev_erase(struct mtd_info *mtd, struct erase_info *erase)
 249 {
 250         int err;
 251         wait_queue_head_t waitq;
 252         DECLARE_WAITQUEUE(wait, current);
 253
 254         /*
 255          * This code was stol^H^H^H^Hinspired by mtdchar.c
 256          */
 257         init_waitqueue_head(&waitq);
 258
 259         erase->mtd = mtd;
 260         erase->callback = concat_erase_callback;
 261         erase->priv = (unsigned long) &waitq;
 262
 263         /*
 264          * FIXME: Allow INTERRUPTIBLE. Which means
 265          * not having the wait_queue head on the stack.
 266          */
 267         err = mtd_erase(mtd, erase);
 268         if (!err) {
 269                 set_current_state(TASK_UNINTERRUPTIBLE);
 270                 add_wait_queue(&waitq, &wait);
 271                 if (erase->state != MTD_ERASE_DONE
 272                     && erase->state != MTD_ERASE_FAILED)
 273                         schedule();
 274                 remove_wait_queue(&waitq, &wait);
 275                 set_current_state(TASK_RUNNING);
 276
 277                 err = (erase->state == MTD_ERASE_FAILED) ? -EIO : 0;
 278         }
 279         return err;
 280 }
 281
 282 static int concat_erase(struct mtd_info *mtd, struct erase_info *instr)
 283 {
 284         struct mtd_concat *concat = CONCAT(mtd);
 285         struct mtd_info *subdev;
 286         int i, err;
 287         uint64_t length, offset = 0;
 288         struct erase_info *erase;
 289
 290         /*
 291          * Check for proper erase block alignment of the to-be-erased area.
 292          * It is easier to do this based on the super device's erase
 293          * region info rather than looking at each particular sub-device
 294          * in turn.
 295          */
 296         if (!concat->mtd.numeraseregions) {
 297                 /* the easy case: device has uniform erase block size */
 298                 if (instr->addr & (concat->mtd.erasesize - 1))
 299                         return -EINVAL;
 300                 if (instr->len & (concat->mtd.erasesize - 1))
 301                         return -EINVAL;
 302         } else {
 303                 /* device has variable erase size */
 304                 struct mtd_erase_region_info *erase_regions =
 305                     concat->mtd.eraseregions;
 306
 307                 /*
 308                  * Find the erase region where the to-be-erased area begins:
 309                  */
 310                 for (i = 0; i < concat->mtd.numeraseregions &&
 311                      instr->addr >= erase_regions[i].offset; i++) ;
 312                 --i;
 313
 314                 /*
 315                  * Now erase_regions[i] is the region in which the
 316                  * to-be-erased area begins. Verify that the starting
 317                  * offset is aligned to this region's erase size:
 318                  */
 319                 if (instr->addr & (erase_regions[i].erasesize - 1))
 320                         return -EINVAL;
 321
 322                 /*
 323                  * now find the erase region where the to-be-erased area ends:
 324                  */
 325                 for (; i < concat->mtd.numeraseregions &&
 326                      (instr->addr + instr->len) >= erase_regions[i].offset;
 327                      ++i) ;
 328                 --i;
 329                 /*
 330                  * check if the ending offset is aligned to this region's erase size
 331                  */
 332                 if ((instr->addr + instr->len) & (erase_regions[i].erasesize -
 333                                                   1))
 334                         return -EINVAL;
 335         }
 336
 337         /* make a local copy of instr to avoid modifying the caller's struct */
 338         erase = kmalloc(sizeof (struct erase_info), GFP_KERNEL);
 339
 340         if (!erase)
 341                 return -ENOMEM;
 342
 343         *erase = *instr;
 344         length = instr->len;
 345
 346         /*
 347          * find the subdevice where the to-be-erased area begins, adjust
 348          * starting offset to be relative to the subdevice start
 349          */
 350         for (i = 0; i < concat->num_subdev; i++) {
 351                 subdev = concat->subdev[i];
 352                 if (subdev->size <= erase->addr) {
 353                         erase->addr -= subdev->size;
 354                         offset += subdev->size;
 355                 } else {
 356                         break;
 357                 }
 358         }
 359
 360         /* must never happen since size limit has been verified above */
 361         BUG_ON(i >= concat->num_subdev);
 362
 363         /* now do the erase: */
 364         err = 0;
 365         for (; length > 0; i++) {
 366                 /* loop for all subdevices affected by this request */
 367                 subdev = concat->subdev[i];     /* get current subdevice */
 368
 369                 /* limit length to subdevice's size: */
 370                 if (erase->addr + length > subdev->size)
 371                         erase->len = subdev->size - erase->addr;
 372                 else
 373                         erase->len = length;
 374
 375                 length -= erase->len;
 376                 if ((err = concat_dev_erase(subdev, erase))) {
 377                         /* sanity check: should never happen since
 378                          * block alignment has been checked above */
 379                         BUG_ON(err == -EINVAL);
 380                         if (erase->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
 381                                 instr->fail_addr = erase->fail_addr + offset;
 382                         break;
 383                 }
 384                 /*
 385                  * erase->addr specifies the offset of the area to be
 386                  * erased *within the current subdevice*. It can be
 387                  * non-zero only the first time through this loop, i.e.
 388                  * for the first subdevice where blocks need to be erased.
 389                  * All the following erases must begin at the start of the
 390                  * current subdevice, i.e. at offset zero.
 391                  */
 392                 erase->addr = 0;
 393                 offset += subdev->size;
 394         }
 395         instr->state = erase->state;
 396         kfree(erase);
 397         if (err)
 398                 return err;
 399
 400         if (instr->callback)
 401                 instr->callback(instr);
 402         return 0;
 403 }
 404
 405 static int concat_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 406 {
 407         struct mtd_concat *concat = CONCAT(mtd);
 408         int i, err = -EINVAL;
 409
 410         for (i = 0; i < concat->num_subdev; i++) {
 411                 struct mtd_info *subdev = concat->subdev[i];
 412                 uint64_t size;
 413
 414                 if (ofs >= subdev->size) {
 415                         size = 0;
 416                         ofs -= subdev->size;
 417                         continue;
 418                 }
 419                 if (ofs + len > subdev->size)
 420                         size = subdev->size - ofs;
 421                 else
 422                         size = len;
 423
 424                 err = mtd_lock(subdev, ofs, size);
 425
 426                 if (err)
 427                         break;
 428
 429                 len -= size;
 430                 if (len == 0)
 431                         break;
 432
 433                 err = -EINVAL;
 434                 ofs = 0;
 435         }
 436
 437         return err;
 438 }
 439
 440 static int concat_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 441 {
 442         struct mtd_concat *concat = CONCAT(mtd);
 443         int i, err = 0;
 444
 445         for (i = 0; i < concat->num_subdev; i++) {
 446                 struct mtd_info *subdev = concat->subdev[i];
 447                 uint64_t size;
 448
 449                 if (ofs >= subdev->size) {
 450                         size = 0;
 451                         ofs -= subdev->size;
 452                         continue;
 453                 }
 454                 if (ofs + len > subdev->size)
 455                         size = subdev->size - ofs;
 456                 else
 457                         size = len;
 458
 459                 err = mtd_unlock(subdev, ofs, size);
 460
 461                 if (err)
 462                         break;
 463
 464                 len -= size;
 465                 if (len == 0)
 466                         break;
 467
 468                 err = -EINVAL;
 469                 ofs = 0;
 470         }
 471
 472         return err;
 473 }
 474
 475 static void concat_sync(struct mtd_info *mtd)
 476 {
 477         struct mtd_concat *concat = CONCAT(mtd);
 478         int i;
 479
 480         for (i = 0; i < concat->num_subdev; i++) {
 481                 struct mtd_info *subdev = concat->subdev[i];
 482                 mtd_sync(subdev);
 483         }
 484 }
 485
 486 static int concat_block_isbad(struct mtd_info *mtd, loff_t ofs)
 487 {
 488         struct mtd_concat *concat = CONCAT(mtd);
 489         int i, res = 0;
 490
 491         if (!mtd_can_have_bb(concat->subdev[0]))
 492                 return res;
 493
 494         for (i = 0; i < concat->num_subdev; i++) {
 495                 struct mtd_info *subdev = concat->subdev[i];
 496
 497                 if (ofs >= subdev->size) {
 498                         ofs -= subdev->size;
 499                         continue;
 500                 }
 501
 502                 res = mtd_block_isbad(subdev, ofs);
 503                 break;
 504         }
 505
 506         return res;
 507 }
 508
 509 static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs)
 510 {
 511         struct mtd_concat *concat = CONCAT(mtd);
 512         int i, err = -EINVAL;
 513
 514         if (!mtd_can_have_bb(concat->subdev[0]))
 515                 return 0;
 516
 517         for (i = 0; i < concat->num_subdev; i++) {
 518                 struct mtd_info *subdev = concat->subdev[i];
 519
 520                 if (ofs >= subdev->size) {
 521                         ofs -= subdev->size;
 522                         continue;
 523                 }
 524
 525                 err = mtd_block_markbad(subdev, ofs);
 526                 if (!err)
 527                         mtd->ecc_stats.badblocks++;
 528                 break;
 529         }
 530
 531         return err;
 532 }
 533
 534 /*
 535  * This function constructs a virtual MTD device by concatenating
 536  * num_devs MTD devices. A pointer to the new device object is
 537  * stored to *new_dev upon success. This function does _not_
 538  * register any devices: this is the caller's responsibility.
 539  */
 540 struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],   /* subdevices to concatenate */
 541                                    int num_devs,        /* number of subdevices      */
 542                                    const char *name)
 543 {                               /* name for the new device   */
 544         int i;
 545         size_t size;
 546         struct mtd_concat *concat;
 547         uint32_t max_erasesize, curr_erasesize;
 548         int num_erase_region;
 549
 550         debug("Concatenating MTD devices:\n");
 551         for (i = 0; i < num_devs; i++)
 552                 debug("(%d): \"%s\"\n", i, subdev[i]->name);
 553         debug("into device \"%s\"\n", name);
 554
 555         /* allocate the device structure */
 556         size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
 557         concat = kzalloc(size, GFP_KERNEL);
 558         if (!concat) {
 559                 printk
 560                     ("memory allocation error while creating concatenated device \"%s\"\n",
 561                      name);
 562                 return NULL;
 563         }
 564         concat->subdev = (struct mtd_info **) (concat + 1);
 565
 566         /*
 567          * Set up the new "super" device's MTD object structure, check for
 568          * incompatibilites between the subdevices.
 569          */
 570         concat->mtd.type = subdev[0]->type;
 571         concat->mtd.flags = subdev[0]->flags;
 572         concat->mtd.size = subdev[0]->size;
 573         concat->mtd.erasesize = subdev[0]->erasesize;
 574         concat->mtd.writesize = subdev[0]->writesize;
 575         concat->mtd.subpage_sft = subdev[0]->subpage_sft;
 576         concat->mtd.oobsize = subdev[0]->oobsize;
 577         concat->mtd.oobavail = subdev[0]->oobavail;
 578         if (subdev[0]->_read_oob)
 579                 concat->mtd._read_oob = concat_read_oob;
 580         if (subdev[0]->_write_oob)
 581                 concat->mtd._write_oob = concat_write_oob;
 582         if (subdev[0]->_block_isbad)
 583                 concat->mtd._block_isbad = concat_block_isbad;
 584         if (subdev[0]->_block_markbad)
 585                 concat->mtd._block_markbad = concat_block_markbad;
 586
 587         concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
 588
 589         concat->subdev[0] = subdev[0];
 590
 591         for (i = 1; i < num_devs; i++) {
 592                 if (concat->mtd.type != subdev[i]->type) {
 593                         kfree(concat);
 594                         printk("Incompatible device type on \"%s\"\n",
 595                                subdev[i]->name);
 596                         return NULL;
 597                 }
 598                 if (concat->mtd.flags != subdev[i]->flags) {
 599                         /*
 600                          * Expect all flags except MTD_WRITEABLE to be
 601                          * equal on all subdevices.
 602                          */
 603                         if ((concat->mtd.flags ^ subdev[i]->
 604                              flags) & ~MTD_WRITEABLE) {
 605                                 kfree(concat);
 606                                 printk("Incompatible device flags on \"%s\"\n",
 607                                        subdev[i]->name);
 608                                 return NULL;
 609                         } else
 610                                 /* if writeable attribute differs,
 611                                    make super device writeable */
 612                                 concat->mtd.flags |=
 613                                     subdev[i]->flags & MTD_WRITEABLE;
 614                 }
 615
 616                 concat->mtd.size += subdev[i]->size;
 617                 concat->mtd.ecc_stats.badblocks +=
 618                         subdev[i]->ecc_stats.badblocks;
 619                 if (concat->mtd.writesize   !=  subdev[i]->writesize ||
 620                     concat->mtd.subpage_sft != subdev[i]->subpage_sft ||
 621                     concat->mtd.oobsize    !=  subdev[i]->oobsize ||
 622                     !concat->mtd._read_oob  != !subdev[i]->_read_oob ||
 623                     !concat->mtd._write_oob != !subdev[i]->_write_oob) {
 624                         kfree(concat);
 625                         printk("Incompatible OOB or ECC data on \"%s\"\n",
 626                                subdev[i]->name);
 627                         return NULL;
 628                 }
 629                 concat->subdev[i] = subdev[i];
 630
 631         }
 632
 633         concat->mtd.ecclayout = subdev[0]->ecclayout;
 634
 635         concat->num_subdev = num_devs;
 636         concat->mtd.name = name;
 637
 638         concat->mtd._erase = concat_erase;
 639         concat->mtd._read = concat_read;
 640         concat->mtd._write = concat_write;
 641         concat->mtd._sync = concat_sync;
 642         concat->mtd._lock = concat_lock;
 643         concat->mtd._unlock = concat_unlock;
 644
 645         /*
 646          * Combine the erase block size info of the subdevices:
 647          *
 648          * first, walk the map of the new device and see how
 649          * many changes in erase size we have
 650          */
 651         max_erasesize = curr_erasesize = subdev[0]->erasesize;
 652         num_erase_region = 1;
 653         for (i = 0; i < num_devs; i++) {
 654                 if (subdev[i]->numeraseregions == 0) {
 655                         /* current subdevice has uniform erase size */
 656                         if (subdev[i]->erasesize != curr_erasesize) {
 657                                 /* if it differs from the last subdevice's erase size, count it */
 658                                 ++num_erase_region;
 659                                 curr_erasesize = subdev[i]->erasesize;
 660                                 if (curr_erasesize > max_erasesize)
 661                                         max_erasesize = curr_erasesize;
 662                         }
 663                 } else {
 664                         /* current subdevice has variable erase size */
 665                         int j;
 666                         for (j = 0; j < subdev[i]->numeraseregions; j++) {
 667
 668                                 /* walk the list of erase regions, count any changes */
 669                                 if (subdev[i]->eraseregions[j].erasesize !=
 670                                     curr_erasesize) {
 671                                         ++num_erase_region;
 672                                         curr_erasesize =
 673                                             subdev[i]->eraseregions[j].
 674                                             erasesize;
 675                                         if (curr_erasesize > max_erasesize)
 676                                                 max_erasesize = curr_erasesize;
 677                                 }
 678                         }
 679                 }
 680         }
 681
 682         if (num_erase_region == 1) {
 683                 /*
 684                  * All subdevices have the same uniform erase size.
 685                  * This is easy:
 686                  */
 687                 concat->mtd.erasesize = curr_erasesize;
 688                 concat->mtd.numeraseregions = 0;
 689         } else {
 690                 uint64_t tmp64;
 691
 692                 /*
 693                  * erase block size varies across the subdevices: allocate
 694                  * space to store the data describing the variable erase regions
 695                  */
 696                 struct mtd_erase_region_info *erase_region_p;
 697                 uint64_t begin, position;
 698
 699                 concat->mtd.erasesize = max_erasesize;
 700                 concat->mtd.numeraseregions = num_erase_region;
 701                 concat->mtd.eraseregions = erase_region_p =
 702                     kmalloc(num_erase_region *
 703                             sizeof (struct mtd_erase_region_info), GFP_KERNEL);
 704                 if (!erase_region_p) {
 705                         kfree(concat);
 706                         printk
 707                             ("memory allocation error while creating erase region list"
 708                              " for device \"%s\"\n", name);
 709                         return NULL;
 710                 }
 711
 712                 /*
 713                  * walk the map of the new device once more and fill in
 714                  * in erase region info:
 715                  */
 716                 curr_erasesize = subdev[0]->erasesize;
 717                 begin = position = 0;
 718                 for (i = 0; i < num_devs; i++) {
 719                         if (subdev[i]->numeraseregions == 0) {
 720                                 /* current subdevice has uniform erase size */
 721                                 if (subdev[i]->erasesize != curr_erasesize) {
 722                                         /*
 723                                          *  fill in an mtd_erase_region_info structure for the area
 724                                          *  we have walked so far:
 725                                          */
 726                                         erase_region_p->offset = begin;
 727                                         erase_region_p->erasesize =
 728                                             curr_erasesize;
 729                                         tmp64 = position - begin;
 730                                         do_div(tmp64, curr_erasesize);
 731                                         erase_region_p->numblocks = tmp64;
 732                                         begin = position;
 733
 734                                         curr_erasesize = subdev[i]->erasesize;
 735                                         ++erase_region_p;
 736                                 }
 737                                 position += subdev[i]->size;
 738                         } else {
 739                                 /* current subdevice has variable erase size */
 740                                 int j;
 741                                 for (j = 0; j < subdev[i]->numeraseregions; j++) {
 742                                         /* walk the list of erase regions, count any changes */
 743                                         if (subdev[i]->eraseregions[j].
 744                                             erasesize != curr_erasesize) {
 745                                                 erase_region_p->offset = begin;
 746                                                 erase_region_p->erasesize =
 747                                                     curr_erasesize;
 748                                                 tmp64 = position - begin;
 749                                                 do_div(tmp64, curr_erasesize);
 750                                                 erase_region_p->numblocks = tmp64;
 751                                                 begin = position;
 752
 753                                                 curr_erasesize =
 754                                                     subdev[i]->eraseregions[j].
 755                                                     erasesize;
 756                                                 ++erase_region_p;
 757                                         }
 758                                         position +=
 759                                             subdev[i]->eraseregions[j].
 760                                             numblocks * (uint64_t)curr_erasesize;
 761                                 }
 762                         }
 763                 }
 764                 /* Now write the final entry */
 765                 erase_region_p->offset = begin;
 766                 erase_region_p->erasesize = curr_erasesize;
 767                 tmp64 = position - begin;
 768                 do_div(tmp64, curr_erasesize);
 769                 erase_region_p->numblocks = tmp64;
 770         }
 771
 772         return &concat->mtd;
 773 }