include/mtd/ubi-header.h

   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  * Authors: Artem Bityutskiy (Битюцкий Артём)
  19  *          Thomas Gleixner
  20  *          Frank Haverkamp
  21  *          Oliver Lohmann
  22  *          Andreas Arnez
  23  */
  24
  25 /*
  26  * This file defines the layout of UBI headers and all the other UBI on-flash
  27  * data structures. May be included by user-space.
  28  */
  29
  30 #ifndef __UBI_HEADER_H__
  31 #define __UBI_HEADER_H__
  32
  33 #include <asm/byteorder.h>
  34
  35 /* The version of UBI images supported by this implementation */
  36 #define UBI_VERSION 1
  37
  38 /* The highest erase counter value supported by this implementation */
  39 #define UBI_MAX_ERASECOUNTER 0x7FFFFFFF
  40
  41 /* The initial CRC32 value used when calculating CRC checksums */
  42 #define UBI_CRC32_INIT 0xFFFFFFFFU
  43
  44 /* Erase counter header magic number (ASCII "UBI#") */
  45 #define UBI_EC_HDR_MAGIC  0x55424923
  46 /* Volume identifier header magic number (ASCII "UBI!") */
  47 #define UBI_VID_HDR_MAGIC 0x55424921
  48
  49 /*
  50  * Volume type constants used in the volume identifier header.
  51  *
  52  * @UBI_VID_DYNAMIC: dynamic volume
  53  * @UBI_VID_STATIC: static volume
  54  */
  55 enum {
  56         UBI_VID_DYNAMIC = 1,
  57         UBI_VID_STATIC  = 2
  58 };
  59
  60 /*
  61  * Compatibility constants used by internal volumes.
  62  *
  63  * @UBI_COMPAT_DELETE: delete this internal volume before anything is written
  64  * to the flash
  65  * @UBI_COMPAT_RO: attach this device in read-only mode
  66  * @UBI_COMPAT_PRESERVE: preserve this internal volume - do not touch its
  67  * physical eraseblocks, don't allow the wear-leveling unit to move them
  68  * @UBI_COMPAT_REJECT: reject this UBI image
  69  */
  70 enum {
  71         UBI_COMPAT_DELETE   = 1,
  72         UBI_COMPAT_RO       = 2,
  73         UBI_COMPAT_PRESERVE = 4,
  74         UBI_COMPAT_REJECT   = 5
  75 };
  76
  77 /* Sizes of UBI headers */
  78 #define UBI_EC_HDR_SIZE  sizeof(struct ubi_ec_hdr)
  79 #define UBI_VID_HDR_SIZE sizeof(struct ubi_vid_hdr)
  80
  81 /* Sizes of UBI headers without the ending CRC */
  82 #define UBI_EC_HDR_SIZE_CRC  (UBI_EC_HDR_SIZE  - sizeof(__be32))
  83 #define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(__be32))
  84
  85 /**
  86  * struct ubi_ec_hdr - UBI erase counter header.
  87  * @magic: erase counter header magic number (%UBI_EC_HDR_MAGIC)
  88  * @version: version of UBI implementation which is supposed to accept this
  89  * UBI image
  90  * @padding1: reserved for future, zeroes
  91  * @ec: the erase counter
  92  * @vid_hdr_offset: where the VID header starts
  93  * @data_offset: where the user data start
  94  * @padding2: reserved for future, zeroes
  95  * @hdr_crc: erase counter header CRC checksum
  96  *
  97  * The erase counter header takes 64 bytes and has a plenty of unused space for
  98  * future usage. The unused fields are zeroed. The @version field is used to
  99  * indicate the version of UBI implementation which is supposed to be able to
 100  * work with this UBI image. If @version is greater then the current UBI
 101  * version, the image is rejected. This may be useful in future if something
 102  * is changed radically. This field is duplicated in the volume identifier
 103  * header.
 104  *
 105  * The @vid_hdr_offset and @data_offset fields contain the offset of the the
 106  * volume identifier header and user data, relative to the beginning of the
 107  * physical eraseblock. These values have to be the same for all physical
 108  * eraseblocks.
 109  */
 110 struct ubi_ec_hdr {
 111         __be32  magic;
 112         __u8    version;
 113         __u8    padding1[3];
 114         __be64  ec; /* Warning: the current limit is 31-bit anyway! */
 115         __be32  vid_hdr_offset;
 116         __be32  data_offset;
 117         __u8    padding2[36];
 118         __be32  hdr_crc;
 119 } __attribute__ ((packed));
 120
 121 /**
 122  * struct ubi_vid_hdr - on-flash UBI volume identifier header.
 123  * @magic: volume identifier header magic number (%UBI_VID_HDR_MAGIC)
 124  * @version: UBI implementation version which is supposed to accept this UBI
 125  * image (%UBI_VERSION)
 126  * @vol_type: volume type (%UBI_VID_DYNAMIC or %UBI_VID_STATIC)
 127  * @copy_flag: if this logical eraseblock was copied from another physical
 128  * eraseblock (for wear-leveling reasons)
 129  * @compat: compatibility of this volume (%0, %UBI_COMPAT_DELETE,
 130  * %UBI_COMPAT_IGNORE, %UBI_COMPAT_PRESERVE, or %UBI_COMPAT_REJECT)
 131  * @vol_id: ID of this volume
 132  * @lnum: logical eraseblock number
 133  * @leb_ver: version of this logical eraseblock (IMPORTANT: obsolete, to be
 134  * removed, kept only for not breaking older UBI users)
 135  * @data_size: how many bytes of data this logical eraseblock contains
 136  * @used_ebs: total number of used logical eraseblocks in this volume
 137  * @data_pad: how many bytes at the end of this physical eraseblock are not
 138  * used
 139  * @data_crc: CRC checksum of the data stored in this logical eraseblock
 140  * @padding1: reserved for future, zeroes
 141  * @sqnum: sequence number
 142  * @padding2: reserved for future, zeroes
 143  * @hdr_crc: volume identifier header CRC checksum
 144  *
 145  * The @sqnum is the value of the global sequence counter at the time when this
 146  * VID header was created. The global sequence counter is incremented each time
 147  * UBI writes a new VID header to the flash, i.e. when it maps a logical
 148  * eraseblock to a new physical eraseblock. The global sequence counter is an
 149  * unsigned 64-bit integer and we assume it never overflows. The @sqnum
 150  * (sequence number) is used to distinguish between older and newer versions of
 151  * logical eraseblocks.
 152  *
 153  * There are 2 situations when there may be more then one physical eraseblock
 154  * corresponding to the same logical eraseblock, i.e., having the same @vol_id
 155  * and @lnum values in the volume identifier header. Suppose we have a logical
 156  * eraseblock L and it is mapped to the physical eraseblock P.
 157  *
 158  * 1. Because UBI may erase physical eraseblocks asynchronously, the following
 159  * situation is possible: L is asynchronously erased, so P is scheduled for
 160  * erasure, then L is written to,i.e. mapped to another physical eraseblock P1,
 161  * so P1 is written to, then an unclean reboot happens. Result - there are 2
 162  * physical eraseblocks P and P1 corresponding to the same logical eraseblock
 163  * L. But P1 has greater sequence number, so UBI picks P1 when it attaches the
 164  * flash.
 165  *
 166  * 2. From time to time UBI moves logical eraseblocks to other physical
 167  * eraseblocks for wear-leveling reasons. If, for example, UBI moves L from P
 168  * to P1, and an unclean reboot happens before P is physically erased, there
 169  * are two physical eraseblocks P and P1 corresponding to L and UBI has to
 170  * select one of them when the flash is attached. The @sqnum field says which
 171  * PEB is the original (obviously P will have lower @sqnum) and the copy. But
 172  * it is not enough to select the physical eraseblock with the higher sequence
 173  * number, because the unclean reboot could have happen in the middle of the
 174  * copying process, so the data in P is corrupted. It is also not enough to
 175  * just select the physical eraseblock with lower sequence number, because the
 176  * data there may be old (consider a case if more data was added to P1 after
 177  * the copying). Moreover, the unclean reboot may happen when the erasure of P
 178  * was just started, so it result in unstable P, which is "mostly" OK, but
 179  * still has unstable bits.
 180  *
 181  * UBI uses the @copy_flag field to indicate that this logical eraseblock is a
 182  * copy. UBI also calculates data CRC when the data is moved and stores it at
 183  * the @data_crc field of the copy (P1). So when UBI needs to pick one physical
 184  * eraseblock of two (P or P1), the @copy_flag of the newer one (P1) is
 185  * examined. If it is cleared, the situation* is simple and the newer one is
 186  * picked. If it is set, the data CRC of the copy (P1) is examined. If the CRC
 187  * checksum is correct, this physical eraseblock is selected (P1). Otherwise
 188  * the older one (P) is selected.
 189  *
 190  * Note, there is an obsolete @leb_ver field which was used instead of @sqnum
 191  * in the past. But it is not used anymore and we keep it in order to be able
 192  * to deal with old UBI images. It will be removed at some point.
 193  *
 194  * There are 2 sorts of volumes in UBI: user volumes and internal volumes.
 195  * Internal volumes are not seen from outside and are used for various internal
 196  * UBI purposes. In this implementation there is only one internal volume - the
 197  * layout volume. Internal volumes are the main mechanism of UBI extensions.
 198  * For example, in future one may introduce a journal internal volume. Internal
 199  * volumes have their own reserved range of IDs.
 200  *
 201  * The @compat field is only used for internal volumes and contains the "degree
 202  * of their compatibility". It is always zero for user volumes. This field
 203  * provides a mechanism to introduce UBI extensions and to be still compatible
 204  * with older UBI binaries. For example, if someone introduced a journal in
 205  * future, he would probably use %UBI_COMPAT_DELETE compatibility for the
 206  * journal volume.  And in this case, older UBI binaries, which know nothing
 207  * about the journal volume, would just delete this volume and work perfectly
 208  * fine. This is similar to what Ext2fs does when it is fed by an Ext3fs image
 209  * - it just ignores the Ext3fs journal.
 210  *
 211  * The @data_crc field contains the CRC checksum of the contents of the logical
 212  * eraseblock if this is a static volume. In case of dynamic volumes, it does
 213  * not contain the CRC checksum as a rule. The only exception is when the
 214  * data of the physical eraseblock was moved by the wear-leveling unit, then
 215  * the wear-leveling unit calculates the data CRC and stores it in the
 216  * @data_crc field. And of course, the @copy_flag is %in this case.
 217  *
 218  * The @data_size field is used only for static volumes because UBI has to know
 219  * how many bytes of data are stored in this eraseblock. For dynamic volumes,
 220  * this field usually contains zero. The only exception is when the data of the
 221  * physical eraseblock was moved to another physical eraseblock for
 222  * wear-leveling reasons. In this case, UBI calculates CRC checksum of the
 223  * contents and uses both @data_crc and @data_size fields. In this case, the
 224  * @data_size field contains data size.
 225  *
 226  * The @used_ebs field is used only for static volumes and indicates how many
 227  * eraseblocks the data of the volume takes. For dynamic volumes this field is
 228  * not used and always contains zero.
 229  *
 230  * The @data_pad is calculated when volumes are created using the alignment
 231  * parameter. So, effectively, the @data_pad field reduces the size of logical
 232  * eraseblocks of this volume. This is very handy when one uses block-oriented
 233  * software (say, cramfs) on top of the UBI volume.
 234  */
 235 struct ubi_vid_hdr {
 236         __be32  magic;
 237         __u8    version;
 238         __u8    vol_type;
 239         __u8    copy_flag;
 240         __u8    compat;
 241         __be32  vol_id;
 242         __be32  lnum;
 243         __be32  leb_ver; /* obsolete, to be removed, don't use */
 244         __be32  data_size;
 245         __be32  used_ebs;
 246         __be32  data_pad;
 247         __be32  data_crc;
 248         __u8    padding1[4];
 249         __be64  sqnum;
 250         __u8    padding2[12];
 251         __be32  hdr_crc;
 252 } __attribute__ ((packed));
 253
 254 /* Internal UBI volumes count */
 255 #define UBI_INT_VOL_COUNT 1
 256
 257 /*
 258  * Starting ID of internal volumes. There is reserved room for 4096 internal
 259  * volumes.
 260  */
 261 #define UBI_INTERNAL_VOL_START (0x7FFFFFFF - 4096)
 262
 263 /* The layout volume contains the volume table */
 264
 265 #define UBI_LAYOUT_VOL_ID        UBI_INTERNAL_VOL_START
 266 #define UBI_LAYOUT_VOLUME_EBS    2
 267 #define UBI_LAYOUT_VOLUME_NAME   "layout volume"
 268 #define UBI_LAYOUT_VOLUME_COMPAT UBI_COMPAT_REJECT
 269
 270 /* The maximum number of volumes per one UBI device */
 271 #define UBI_MAX_VOLUMES 128
 272
 273 /* The maximum volume name length */
 274 #define UBI_VOL_NAME_MAX 127
 275
 276 /* Size of the volume table record */
 277 #define UBI_VTBL_RECORD_SIZE sizeof(struct ubi_vtbl_record)
 278
 279 /* Size of the volume table record without the ending CRC */
 280 #define UBI_VTBL_RECORD_SIZE_CRC (UBI_VTBL_RECORD_SIZE - sizeof(__be32))
 281
 282 /**
 283  * struct ubi_vtbl_record - a record in the volume table.
 284  * @reserved_pebs: how many physical eraseblocks are reserved for this volume
 285  * @alignment: volume alignment
 286  * @data_pad: how many bytes are unused at the end of the each physical
 287  * eraseblock to satisfy the requested alignment
 288  * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
 289  * @upd_marker: if volume update was started but not finished
 290  * @name_len: volume name length
 291  * @name: the volume name
 292  * @padding2: reserved, zeroes
 293  * @crc: a CRC32 checksum of the record
 294  *
 295  * The volume table records are stored in the volume table, which is stored in
 296  * the layout volume. The layout volume consists of 2 logical eraseblock, each
 297  * of which contains a copy of the volume table (i.e., the volume table is
 298  * duplicated). The volume table is an array of &struct ubi_vtbl_record
 299  * objects indexed by the volume ID.
 300  *
 301  * If the size of the logical eraseblock is large enough to fit
 302  * %UBI_MAX_VOLUMES records, the volume table contains %UBI_MAX_VOLUMES
 303  * records. Otherwise, it contains as many records as it can fit (i.e., size of
 304  * logical eraseblock divided by sizeof(struct ubi_vtbl_record)).
 305  *
 306  * The @upd_marker flag is used to implement volume update. It is set to %1
 307  * before update and set to %0 after the update. So if the update operation was
 308  * interrupted, UBI knows that the volume is corrupted.
 309  *
 310  * The @alignment field is specified when the volume is created and cannot be
 311  * later changed. It may be useful, for example, when a block-oriented file
 312  * system works on top of UBI. The @data_pad field is calculated using the
 313  * logical eraseblock size and @alignment. The alignment must be multiple to the
 314  * minimal flash I/O unit. If @alignment is 1, all the available space of
 315  * the physical eraseblocks is used.
 316  *
 317  * Empty records contain all zeroes and the CRC checksum of those zeroes.
 318  */
 319 struct ubi_vtbl_record {
 320         __be32  reserved_pebs;
 321         __be32  alignment;
 322         __be32  data_pad;
 323         __u8    vol_type;
 324         __u8    upd_marker;
 325         __be16  name_len;
 326         __u8    name[UBI_VOL_NAME_MAX+1];
 327         __u8    padding2[24];
 328         __be32  crc;
 329 } __attribute__ ((packed));
 330
 331 #endif /* !__UBI_HEADER_H__ */