drivers/mtd/ubi/cdev.c

   1 /*
   2  * Copyright (c) International Business Machines Corp., 2006
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
  12  * the GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  17  *
  18  * Author: Artem Bityutskiy (Битюцкий Артём)
  19  */
  20
  21 /*
  22  * This file includes implementation of UBI character device operations.
  23  *
  24  * There are two kinds of character devices in UBI: UBI character devices and
  25  * UBI volume character devices. UBI character devices allow users to
  26  * manipulate whole volumes: create, remove, and re-size them. Volume character
  27  * devices provide volume I/O capabilities.
  28  *
  29  * Major and minor numbers are assigned dynamically to both UBI and volume
  30  * character devices.
  31  *
  32  * Well, there is the third kind of character devices - the UBI control
  33  * character device, which allows to manipulate by UBI devices - create and
  34  * delete them. In other words, it is used for attaching and detaching MTD
  35  * devices.
  36  */
  37
  38 #include <linux/module.h>
  39 #include <linux/stat.h>
  40 #include <linux/ioctl.h>
  41 #include <linux/capability.h>
  42 #include <mtd/ubi-user.h>
  43 #include <asm/uaccess.h>
  44 #include <asm/div64.h>
  45 #include "ubi.h"
  46
  47 /**
  48  * get_exclusive - get exclusive access to an UBI volume.
  49  * @desc: volume descriptor
  50  *
  51  * This function changes UBI volume open mode to "exclusive". Returns previous
  52  * mode value (positive integer) in case of success and a negative error code
  53  * in case of failure.
  54  */
  55 static int get_exclusive(struct ubi_volume_desc *desc)
  56 {
  57         int users, err;
  58         struct ubi_volume *vol = desc->vol;
  59
  60         spin_lock(&vol->ubi->volumes_lock);
  61         users = vol->readers + vol->writers + vol->exclusive;
  62         ubi_assert(users > 0);
  63         if (users > 1) {
  64                 dbg_err("%d users for volume %d", users, vol->vol_id);
  65                 err = -EBUSY;
  66         } else {
  67                 vol->readers = vol->writers = 0;
  68                 vol->exclusive = 1;
  69                 err = desc->mode;
  70                 desc->mode = UBI_EXCLUSIVE;
  71         }
  72         spin_unlock(&vol->ubi->volumes_lock);
  73
  74         return err;
  75 }
  76
  77 /**
  78  * revoke_exclusive - revoke exclusive mode.
  79  * @desc: volume descriptor
  80  * @mode: new mode to switch to
  81  */
  82 static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
  83 {
  84         struct ubi_volume *vol = desc->vol;
  85
  86         spin_lock(&vol->ubi->volumes_lock);
  87         ubi_assert(vol->readers == 0 && vol->writers == 0);
  88         ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
  89         vol->exclusive = 0;
  90         if (mode == UBI_READONLY)
  91                 vol->readers = 1;
  92         else if (mode == UBI_READWRITE)
  93                 vol->writers = 1;
  94         else
  95                 vol->exclusive = 1;
  96         spin_unlock(&vol->ubi->volumes_lock);
  97
  98         desc->mode = mode;
  99 }
 100
 101 static int vol_cdev_open(struct inode *inode, struct file *file)
 102 {
 103         struct ubi_volume_desc *desc;
 104         int vol_id = iminor(inode) - 1, mode, ubi_num;
 105
 106         ubi_num = ubi_major2num(imajor(inode));
 107         if (ubi_num < 0)
 108                 return ubi_num;
 109
 110         if (file->f_mode & FMODE_WRITE)
 111                 mode = UBI_READWRITE;
 112         else
 113                 mode = UBI_READONLY;
 114
 115         dbg_msg("open volume %d, mode %d", vol_id, mode);
 116
 117         desc = ubi_open_volume(ubi_num, vol_id, mode);
 118         if (IS_ERR(desc))
 119                 return PTR_ERR(desc);
 120
 121         file->private_data = desc;
 122         return 0;
 123 }
 124
 125 static int vol_cdev_release(struct inode *inode, struct file *file)
 126 {
 127         struct ubi_volume_desc *desc = file->private_data;
 128         struct ubi_volume *vol = desc->vol;
 129
 130         dbg_msg("release volume %d, mode %d", vol->vol_id, desc->mode);
 131
 132         if (vol->updating) {
 133                 ubi_warn("update of volume %d not finished, volume is damaged",
 134                          vol->vol_id);
 135                 ubi_assert(!vol->changing_leb);
 136                 vol->updating = 0;
 137                 vfree(vol->upd_buf);
 138         } else if (vol->changing_leb) {
 139                 dbg_msg("only %lld of %lld bytes received for atomic LEB change"
 140                         " for volume %d:%d, cancel", vol->upd_received,
 141                         vol->upd_bytes, vol->ubi->ubi_num, vol->vol_id);
 142                 vol->changing_leb = 0;
 143                 vfree(vol->upd_buf);
 144         }
 145
 146         ubi_close_volume(desc);
 147         return 0;
 148 }
 149
 150 static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
 151 {
 152         struct ubi_volume_desc *desc = file->private_data;
 153         struct ubi_volume *vol = desc->vol;
 154         loff_t new_offset;
 155
 156         if (vol->updating) {
 157                  /* Update is in progress, seeking is prohibited */
 158                 dbg_err("updating");
 159                 return -EBUSY;
 160         }
 161
 162         switch (origin) {
 163         case 0: /* SEEK_SET */
 164                 new_offset = offset;
 165                 break;
 166         case 1: /* SEEK_CUR */
 167                 new_offset = file->f_pos + offset;
 168                 break;
 169         case 2: /* SEEK_END */
 170                 new_offset = vol->used_bytes + offset;
 171                 break;
 172         default:
 173                 return -EINVAL;
 174         }
 175
 176         if (new_offset < 0 || new_offset > vol->used_bytes) {
 177                 dbg_err("bad seek %lld", new_offset);
 178                 return -EINVAL;
 179         }
 180
 181         dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
 182                 vol->vol_id, offset, origin, new_offset);
 183
 184         file->f_pos = new_offset;
 185         return new_offset;
 186 }
 187
 188 static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
 189                              loff_t *offp)
 190 {
 191         struct ubi_volume_desc *desc = file->private_data;
 192         struct ubi_volume *vol = desc->vol;
 193         struct ubi_device *ubi = vol->ubi;
 194         int err, lnum, off, len,  tbuf_size;
 195         size_t count_save = count;
 196         void *tbuf;
 197         uint64_t tmp;
 198
 199         dbg_msg("read %zd bytes from offset %lld of volume %d",
 200                 count, *offp, vol->vol_id);
 201
 202         if (vol->updating) {
 203                 dbg_err("updating");
 204                 return -EBUSY;
 205         }
 206         if (vol->upd_marker) {
 207                 dbg_err("damaged volume, update marker is set");
 208                 return -EBADF;
 209         }
 210         if (*offp == vol->used_bytes || count == 0)
 211                 return 0;
 212
 213         if (vol->corrupted)
 214                 dbg_msg("read from corrupted volume %d", vol->vol_id);
 215
 216         if (*offp + count > vol->used_bytes)
 217                 count_save = count = vol->used_bytes - *offp;
 218
 219         tbuf_size = vol->usable_leb_size;
 220         if (count < tbuf_size)
 221                 tbuf_size = ALIGN(count, ubi->min_io_size);
 222         tbuf = vmalloc(tbuf_size);
 223         if (!tbuf)
 224                 return -ENOMEM;
 225
 226         len = count > tbuf_size ? tbuf_size : count;
 227
 228         tmp = *offp;
 229         off = do_div(tmp, vol->usable_leb_size);
 230         lnum = tmp;
 231
 232         do {
 233                 cond_resched();
 234
 235                 if (off + len >= vol->usable_leb_size)
 236                         len = vol->usable_leb_size - off;
 237
 238                 err = ubi_eba_read_leb(ubi, vol, lnum, tbuf, off, len, 0);
 239                 if (err)
 240                         break;
 241
 242                 off += len;
 243                 if (off == vol->usable_leb_size) {
 244                         lnum += 1;
 245                         off -= vol->usable_leb_size;
 246                 }
 247
 248                 count -= len;
 249                 *offp += len;
 250
 251                 err = copy_to_user(buf, tbuf, len);
 252                 if (err) {
 253                         err = -EFAULT;
 254                         break;
 255                 }
 256
 257                 buf += len;
 258                 len = count > tbuf_size ? tbuf_size : count;
 259         } while (count);
 260
 261         vfree(tbuf);
 262         return err ? err : count_save - count;
 263 }
 264
 265 #ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
 266
 267 /*
 268  * This function allows to directly write to dynamic UBI volumes, without
 269  * issuing the volume update operation. Available only as a debugging feature.
 270  * Very useful for testing UBI.
 271  */
 272 static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
 273                                      size_t count, loff_t *offp)
 274 {
 275         struct ubi_volume_desc *desc = file->private_data;
 276         struct ubi_volume *vol = desc->vol;
 277         struct ubi_device *ubi = vol->ubi;
 278         int lnum, off, len, tbuf_size, err = 0;
 279         size_t count_save = count;
 280         char *tbuf;
 281         uint64_t tmp;
 282
 283         dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
 284                 count, *offp, vol->vol_id);
 285
 286         if (vol->vol_type == UBI_STATIC_VOLUME)
 287                 return -EROFS;
 288
 289         tmp = *offp;
 290         off = do_div(tmp, vol->usable_leb_size);
 291         lnum = tmp;
 292
 293         if (off % ubi->min_io_size) {
 294                 dbg_err("unaligned position");
 295                 return -EINVAL;
 296         }
 297
 298         if (*offp + count > vol->used_bytes)
 299                 count_save = count = vol->used_bytes - *offp;
 300
 301         /* We can write only in fractions of the minimum I/O unit */
 302         if (count % ubi->min_io_size) {
 303                 dbg_err("unaligned write length");
 304                 return -EINVAL;
 305         }
 306
 307         tbuf_size = vol->usable_leb_size;
 308         if (count < tbuf_size)
 309                 tbuf_size = ALIGN(count, ubi->min_io_size);
 310         tbuf = vmalloc(tbuf_size);
 311         if (!tbuf)
 312                 return -ENOMEM;
 313
 314         len = count > tbuf_size ? tbuf_size : count;
 315
 316         while (count) {
 317                 cond_resched();
 318
 319                 if (off + len >= vol->usable_leb_size)
 320                         len = vol->usable_leb_size - off;
 321
 322                 err = copy_from_user(tbuf, buf, len);
 323                 if (err) {
 324                         err = -EFAULT;
 325                         break;
 326                 }
 327
 328                 err = ubi_eba_write_leb(ubi, vol, lnum, tbuf, off, len,
 329                                         UBI_UNKNOWN);
 330                 if (err)
 331                         break;
 332
 333                 off += len;
 334                 if (off == vol->usable_leb_size) {
 335                         lnum += 1;
 336                         off -= vol->usable_leb_size;
 337                 }
 338
 339                 count -= len;
 340                 *offp += len;
 341                 buf += len;
 342                 len = count > tbuf_size ? tbuf_size : count;
 343         }
 344
 345         vfree(tbuf);
 346         return err ? err : count_save - count;
 347 }
 348
 349 #else
 350 #define vol_cdev_direct_write(file, buf, count, offp) -EPERM
 351 #endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */
 352
 353 static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
 354                               size_t count, loff_t *offp)
 355 {
 356         int err = 0;
 357         struct ubi_volume_desc *desc = file->private_data;
 358         struct ubi_volume *vol = desc->vol;
 359         struct ubi_device *ubi = vol->ubi;
 360
 361         if (!vol->updating && !vol->changing_leb)
 362                 return vol_cdev_direct_write(file, buf, count, offp);
 363
 364         if (vol->updating)
 365                 err = ubi_more_update_data(ubi, vol, buf, count);
 366         else
 367                 err = ubi_more_leb_change_data(ubi, vol, buf, count);
 368
 369         if (err < 0) {
 370                 ubi_err("cannot accept more %zd bytes of data, error %d",
 371                         count, err);
 372                 return err;
 373         }
 374
 375         if (err) {
 376                 /*
 377                  * The operation is finished, @err contains number of actually
 378                  * written bytes.
 379                  */
 380                 count = err;
 381
 382                 if (vol->changing_leb) {
 383                         revoke_exclusive(desc, UBI_READWRITE);
 384                         return count;
 385                 }
 386
 387                 err = ubi_check_volume(ubi, vol->vol_id);
 388                 if (err < 0)
 389                         return err;
 390
 391                 if (err) {
 392                         ubi_warn("volume %d on UBI device %d is corrupted",
 393                                  vol->vol_id, ubi->ubi_num);
 394                         vol->corrupted = 1;
 395                 }
 396                 vol->checked = 1;
 397                 ubi_gluebi_updated(vol);
 398                 revoke_exclusive(desc, UBI_READWRITE);
 399         }
 400
 401         return count;
 402 }
 403
 404 static int vol_cdev_ioctl(struct inode *inode, struct file *file,
 405                           unsigned int cmd, unsigned long arg)
 406 {
 407         int err = 0;
 408         struct ubi_volume_desc *desc = file->private_data;
 409         struct ubi_volume *vol = desc->vol;
 410         struct ubi_device *ubi = vol->ubi;
 411         void __user *argp = (void __user *)arg;
 412
 413         switch (cmd) {
 414         /* Volume update command */
 415         case UBI_IOCVOLUP:
 416         {
 417                 int64_t bytes, rsvd_bytes;
 418
 419                 if (!capable(CAP_SYS_RESOURCE)) {
 420                         err = -EPERM;
 421                         break;
 422                 }
 423
 424                 err = copy_from_user(&bytes, argp, sizeof(int64_t));
 425                 if (err) {
 426                         err = -EFAULT;
 427                         break;
 428                 }
 429
 430                 if (desc->mode == UBI_READONLY) {
 431                         err = -EROFS;
 432                         break;
 433                 }
 434
 435                 rsvd_bytes = vol->reserved_pebs * (ubi->leb_size-vol->data_pad);
 436                 if (bytes < 0 || bytes > rsvd_bytes) {
 437                         err = -EINVAL;
 438                         break;
 439                 }
 440
 441                 err = get_exclusive(desc);
 442                 if (err < 0)
 443                         break;
 444
 445                 err = ubi_start_update(ubi, vol, bytes);
 446                 if (bytes == 0)
 447                         revoke_exclusive(desc, UBI_READWRITE);
 448                 break;
 449         }
 450
 451         /* Atomic logical eraseblock change command */
 452         case UBI_IOCEBCH:
 453         {
 454                 struct ubi_leb_change_req req;
 455
 456                 err = copy_from_user(&req, argp,
 457                                      sizeof(struct ubi_leb_change_req));
 458                 if (err) {
 459                         err = -EFAULT;
 460                         break;
 461                 }
 462
 463                 if (desc->mode == UBI_READONLY ||
 464                     vol->vol_type == UBI_STATIC_VOLUME) {
 465                         err = -EROFS;
 466                         break;
 467                 }
 468
 469                 /* Validate the request */
 470                 err = -EINVAL;
 471                 if (req.lnum < 0 || req.lnum >= vol->reserved_pebs ||
 472                     req.bytes < 0 || req.lnum >= vol->usable_leb_size)
 473                         break;
 474                 if (req.dtype != UBI_LONGTERM && req.dtype != UBI_SHORTTERM &&
 475                     req.dtype != UBI_UNKNOWN)
 476                         break;
 477
 478                 err = get_exclusive(desc);
 479                 if (err < 0)
 480                         break;
 481
 482                 err = ubi_start_leb_change(ubi, vol, &req);
 483                 if (req.bytes == 0)
 484                         revoke_exclusive(desc, UBI_READWRITE);
 485                 break;
 486         }
 487
 488 #ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
 489         /* Logical eraseblock erasure command */
 490         case UBI_IOCEBER:
 491         {
 492                 int32_t lnum;
 493
 494                 err = get_user(lnum, (__user int32_t *)argp);
 495                 if (err) {
 496                         err = -EFAULT;
 497                         break;
 498                 }
 499
 500                 if (desc->mode == UBI_READONLY ||
 501                     vol->vol_type == UBI_STATIC_VOLUME) {
 502                         err = -EROFS;
 503                         break;
 504                 }
 505
 506                 if (lnum < 0 || lnum >= vol->reserved_pebs) {
 507                         err = -EINVAL;
 508                         break;
 509                 }
 510
 511                 dbg_msg("erase LEB %d:%d", vol->vol_id, lnum);
 512                 err = ubi_eba_unmap_leb(ubi, vol, lnum);
 513                 if (err)
 514                         break;
 515
 516                 err = ubi_wl_flush(ubi);
 517                 break;
 518         }
 519 #endif
 520
 521         default:
 522                 err = -ENOTTY;
 523                 break;
 524         }
 525
 526         return err;
 527 }
 528
 529 /**
 530  * verify_mkvol_req - verify volume creation request.
 531  * @ubi: UBI device description object
 532  * @req: the request to check
 533  *
 534  * This function zero if the request is correct, and %-EINVAL if not.
 535  */
 536 static int verify_mkvol_req(const struct ubi_device *ubi,
 537                             const struct ubi_mkvol_req *req)
 538 {
 539         int n, err = -EINVAL;
 540
 541         if (req->bytes < 0 || req->alignment < 0 || req->vol_type < 0 ||
 542             req->name_len < 0)
 543                 goto bad;
 544
 545         if ((req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots) &&
 546             req->vol_id != UBI_VOL_NUM_AUTO)
 547                 goto bad;
 548
 549         if (req->alignment == 0)
 550                 goto bad;
 551
 552         if (req->bytes == 0)
 553                 goto bad;
 554
 555         if (req->vol_type != UBI_DYNAMIC_VOLUME &&
 556             req->vol_type != UBI_STATIC_VOLUME)
 557                 goto bad;
 558
 559         if (req->alignment > ubi->leb_size)
 560                 goto bad;
 561
 562         n = req->alignment % ubi->min_io_size;
 563         if (req->alignment != 1 && n)
 564                 goto bad;
 565
 566         if (req->name_len > UBI_VOL_NAME_MAX) {
 567                 err = -ENAMETOOLONG;
 568                 goto bad;
 569         }
 570
 571         return 0;
 572
 573 bad:
 574         dbg_err("bad volume creation request");
 575         ubi_dbg_dump_mkvol_req(req);
 576         return err;
 577 }
 578
 579 /**
 580  * verify_rsvol_req - verify volume re-size request.
 581  * @ubi: UBI device description object
 582  * @req: the request to check
 583  *
 584  * This function returns zero if the request is correct, and %-EINVAL if not.
 585  */
 586 static int verify_rsvol_req(const struct ubi_device *ubi,
 587                             const struct ubi_rsvol_req *req)
 588 {
 589         if (req->bytes <= 0)
 590                 return -EINVAL;
 591
 592         if (req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots)
 593                 return -EINVAL;
 594
 595         return 0;
 596 }
 597
 598 static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
 599                           unsigned int cmd, unsigned long arg)
 600 {
 601         int err = 0;
 602         struct ubi_device *ubi;
 603         struct ubi_volume_desc *desc;
 604         void __user *argp = (void __user *)arg;
 605
 606         if (!capable(CAP_SYS_RESOURCE))
 607                 return -EPERM;
 608
 609         ubi = ubi_get_by_major(imajor(inode));
 610         if (!ubi)
 611                 return -ENODEV;
 612
 613         switch (cmd) {
 614         /* Create volume command */
 615         case UBI_IOCMKVOL:
 616         {
 617                 struct ubi_mkvol_req req;
 618
 619                 dbg_msg("create volume");
 620                 err = copy_from_user(&req, argp, sizeof(struct ubi_mkvol_req));
 621                 if (err) {
 622                         err = -EFAULT;
 623                         break;
 624                 }
 625
 626                 err = verify_mkvol_req(ubi, &req);
 627                 if (err)
 628                         break;
 629
 630                 req.name[req.name_len] = '\0';
 631
 632                 mutex_lock(&ubi->volumes_mutex);
 633                 err = ubi_create_volume(ubi, &req);
 634                 mutex_unlock(&ubi->volumes_mutex);
 635                 if (err)
 636                         break;
 637
 638                 err = put_user(req.vol_id, (__user int32_t *)argp);
 639                 if (err)
 640                         err = -EFAULT;
 641
 642                 break;
 643         }
 644
 645         /* Remove volume command */
 646         case UBI_IOCRMVOL:
 647         {
 648                 int vol_id;
 649
 650                 dbg_msg("remove volume");
 651                 err = get_user(vol_id, (__user int32_t *)argp);
 652                 if (err) {
 653                         err = -EFAULT;
 654                         break;
 655                 }
 656
 657                 desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_EXCLUSIVE);
 658                 if (IS_ERR(desc)) {
 659                         err = PTR_ERR(desc);
 660                         break;
 661                 }
 662
 663                 mutex_lock(&ubi->volumes_mutex);
 664                 err = ubi_remove_volume(desc);
 665                 mutex_unlock(&ubi->volumes_mutex);
 666
 667                 /*
 668                  * The volume is deleted (unless an error occurred), and the
 669                  * 'struct ubi_volume' object will be freed when
 670                  * 'ubi_close_volume()' will call 'put_device()'.
 671                  */
 672                 ubi_close_volume(desc);
 673                 break;
 674         }
 675
 676         /* Re-size volume command */
 677         case UBI_IOCRSVOL:
 678         {
 679                 int pebs;
 680                 uint64_t tmp;
 681                 struct ubi_rsvol_req req;
 682
 683                 dbg_msg("re-size volume");
 684                 err = copy_from_user(&req, argp, sizeof(struct ubi_rsvol_req));
 685                 if (err) {
 686                         err = -EFAULT;
 687                         break;
 688                 }
 689
 690                 err = verify_rsvol_req(ubi, &req);
 691                 if (err)
 692                         break;
 693
 694                 desc = ubi_open_volume(ubi->ubi_num, req.vol_id, UBI_EXCLUSIVE);
 695                 if (IS_ERR(desc)) {
 696                         err = PTR_ERR(desc);
 697                         break;
 698                 }
 699
 700                 tmp = req.bytes;
 701                 pebs = !!do_div(tmp, desc->vol->usable_leb_size);
 702                 pebs += tmp;
 703
 704                 mutex_lock(&ubi->volumes_mutex);
 705                 err = ubi_resize_volume(desc, pebs);
 706                 mutex_unlock(&ubi->volumes_mutex);
 707                 ubi_close_volume(desc);
 708                 break;
 709         }
 710
 711         default:
 712                 err = -ENOTTY;
 713                 break;
 714         }
 715
 716         ubi_put_device(ubi);
 717         return err;
 718 }
 719
 720 static int ctrl_cdev_ioctl(struct inode *inode, struct file *file,
 721                            unsigned int cmd, unsigned long arg)
 722 {
 723         int err = 0;
 724         void __user *argp = (void __user *)arg;
 725
 726         if (!capable(CAP_SYS_RESOURCE))
 727                 return -EPERM;
 728
 729         switch (cmd) {
 730         /* Attach an MTD device command */
 731         case UBI_IOCATT:
 732         {
 733                 struct ubi_attach_req req;
 734                 struct mtd_info *mtd;
 735
 736                 dbg_msg("attach MTD device");
 737                 err = copy_from_user(&req, argp, sizeof(struct ubi_attach_req));
 738                 if (err) {
 739                         err = -EFAULT;
 740                         break;
 741                 }
 742
 743                 if (req.mtd_num < 0 ||
 744                     (req.ubi_num < 0 && req.ubi_num != UBI_DEV_NUM_AUTO)) {
 745                         err = -EINVAL;
 746                         break;
 747                 }
 748
 749                 mtd = get_mtd_device(NULL, req.mtd_num);
 750                 if (IS_ERR(mtd)) {
 751                         err = PTR_ERR(mtd);
 752                         break;
 753                 }
 754
 755                 /*
 756                  * Note, further request verification is done by
 757                  * 'ubi_attach_mtd_dev()'.
 758                  */
 759                 mutex_lock(&ubi_devices_mutex);
 760                 err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset);
 761                 mutex_unlock(&ubi_devices_mutex);
 762                 if (err < 0)
 763                         put_mtd_device(mtd);
 764                 else
 765                         /* @err contains UBI device number */
 766                         err = put_user(err, (__user int32_t *)argp);
 767
 768                 break;
 769         }
 770
 771         /* Detach an MTD device command */
 772         case UBI_IOCDET:
 773         {
 774                 int ubi_num;
 775
 776                 dbg_msg("dettach MTD device");
 777                 err = get_user(ubi_num, (__user int32_t *)argp);
 778                 if (err) {
 779                         err = -EFAULT;
 780                         break;
 781                 }
 782
 783                 mutex_lock(&ubi_devices_mutex);
 784                 err = ubi_detach_mtd_dev(ubi_num, 0);
 785                 mutex_unlock(&ubi_devices_mutex);
 786                 break;
 787         }
 788
 789         default:
 790                 err = -ENOTTY;
 791                 break;
 792         }
 793
 794         return err;
 795 }
 796
 797 /* UBI control character device operations */
 798 struct file_operations ubi_ctrl_cdev_operations = {
 799         .ioctl = ctrl_cdev_ioctl,
 800         .owner = THIS_MODULE,
 801 };
 802
 803 /* UBI character device operations */
 804 struct file_operations ubi_cdev_operations = {
 805         .owner = THIS_MODULE,
 806         .ioctl = ubi_cdev_ioctl,
 807         .llseek = no_llseek,
 808 };
 809
 810 /* UBI volume character device operations */
 811 struct file_operations ubi_vol_cdev_operations = {
 812         .owner   = THIS_MODULE,
 813         .open    = vol_cdev_open,
 814         .release = vol_cdev_release,
 815         .llseek  = vol_cdev_llseek,
 816         .read    = vol_cdev_read,
 817         .write   = vol_cdev_write,
 818         .ioctl   = vol_cdev_ioctl,
 819 };