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* Copyright (c) International Business Machines Corp., 2006
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* the GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
* Authors: Artem Bityutskiy (Битюцкий Артём)
* Thomas Gleixner
* Frank Haverkamp
* Oliver Lohmann
* Andreas Arnez
* This file defines the layout of UBI headers and all the other UBI on-flash
* data structures. May be included by user-space.
#ifndef __UBI_HEADER_H__
#define __UBI_HEADER_H__
#include <asm/byteorder.h>
/* The version of UBI images supported by this implementation */
#define UBI_VERSION 1
/* The highest erase counter value supported by this implementation */
/* The initial CRC32 value used when calculating CRC checksums */
/* Erase counter header magic number (ASCII "UBI#") */
#define UBI_EC_HDR_MAGIC 0x55424923
/* Volume identifier header magic number (ASCII "UBI!") */
#define UBI_VID_HDR_MAGIC 0x55424921
* Volume type constants used in the volume identifier header.
* @UBI_VID_DYNAMIC: dynamic volume
* @UBI_VID_STATIC: static volume
enum {
* Compatibility constants used by internal volumes.
* @UBI_COMPAT_DELETE: delete this internal volume before anything is written
* to the flash
* @UBI_COMPAT_RO: attach this device in read-only mode
* @UBI_COMPAT_PRESERVE: preserve this internal volume - do not touch its
* physical eraseblocks, don't allow the wear-leveling unit to move them
* @UBI_COMPAT_REJECT: reject this UBI image
enum {
/* Sizes of UBI headers */
#define UBI_EC_HDR_SIZE sizeof(struct ubi_ec_hdr)
#define UBI_VID_HDR_SIZE sizeof(struct ubi_vid_hdr)
/* Sizes of UBI headers without the ending CRC */
#define UBI_EC_HDR_SIZE_CRC (UBI_EC_HDR_SIZE - sizeof(__be32))
#define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(__be32))
* struct ubi_ec_hdr - UBI erase counter header.
* @magic: erase counter header magic number (%UBI_EC_HDR_MAGIC)
* @version: version of UBI implementation which is supposed to accept this
* UBI image
* @padding1: reserved for future, zeroes
* @ec: the erase counter
* @vid_hdr_offset: where the VID header starts
* @data_offset: where the user data start
* @padding2: reserved for future, zeroes
* @hdr_crc: erase counter header CRC checksum
* The erase counter header takes 64 bytes and has a plenty of unused space for
* future usage. The unused fields are zeroed. The @version field is used to
* indicate the version of UBI implementation which is supposed to be able to
* work with this UBI image. If @version is greater then the current UBI
* version, the image is rejected. This may be useful in future if something
* is changed radically. This field is duplicated in the volume identifier
* header.
* The @vid_hdr_offset and @data_offset fields contain the offset of the the
* volume identifier header and user data, relative to the beginning of the
* physical eraseblock. These values have to be the same for all physical
* eraseblocks.
struct ubi_ec_hdr {
__be32 magic;
__u8 version;
__u8 padding1[3];
__be64 ec; /* Warning: the current limit is 31-bit anyway! */
__be32 vid_hdr_offset;
__be32 data_offset;
__u8 padding2[36];
__be32 hdr_crc;
} __attribute__ ((packed));
* struct ubi_vid_hdr - on-flash UBI volume identifier header.
* @magic: volume identifier header magic number (%UBI_VID_HDR_MAGIC)
* @version: UBI implementation version which is supposed to accept this UBI
* image (%UBI_VERSION)
* @vol_type: volume type (%UBI_VID_DYNAMIC or %UBI_VID_STATIC)
* @copy_flag: if this logical eraseblock was copied from another physical
* eraseblock (for wear-leveling reasons)
* @compat: compatibility of this volume (%0, %UBI_COMPAT_DELETE,
* @vol_id: ID of this volume
* @lnum: logical eraseblock number
* @leb_ver: version of this logical eraseblock (IMPORTANT: obsolete, to be
* removed, kept only for not breaking older UBI users)
* @data_size: how many bytes of data this logical eraseblock contains
* @used_ebs: total number of used logical eraseblocks in this volume
* @data_pad: how many bytes at the end of this physical eraseblock are not
* used
* @data_crc: CRC checksum of the data stored in this logical eraseblock
* @padding1: reserved for future, zeroes
* @sqnum: sequence number
* @padding2: reserved for future, zeroes
* @hdr_crc: volume identifier header CRC checksum
* The @sqnum is the value of the global sequence counter at the time when this
* VID header was created. The global sequence counter is incremented each time
* UBI writes a new VID header to the flash, i.e. when it maps a logical
* eraseblock to a new physical eraseblock. The global sequence counter is an
* unsigned 64-bit integer and we assume it never overflows. The @sqnum
* (sequence number) is used to distinguish between older and newer versions of
* logical eraseblocks.
* There are 2 situations when there may be more then one physical eraseblock
* corresponding to the same logical eraseblock, i.e., having the same @vol_id
* and @lnum values in the volume identifier header. Suppose we have a logical
* eraseblock L and it is mapped to the physical eraseblock P.
* 1. Because UBI may erase physical eraseblocks asynchronously, the following
* situation is possible: L is asynchronously erased, so P is scheduled for
* erasure, then L is written to,i.e. mapped to another physical eraseblock P1,
* so P1 is written to, then an unclean reboot happens. Result - there are 2
* physical eraseblocks P and P1 corresponding to the same logical eraseblock
* L. But P1 has greater sequence number, so UBI picks P1 when it attaches the
* flash.
* 2. From time to time UBI moves logical eraseblocks to other physical
* eraseblocks for wear-leveling reasons. If, for example, UBI moves L from P
* to P1, and an unclean reboot happens before P is physically erased, there
* are two physical eraseblocks P and P1 corresponding to L and UBI has to
* select one of them when the flash is attached. The @sqnum field says which
* PEB is the original (obviously P will have lower @sqnum) and the copy. But
* it is not enough to select the physical eraseblock with the higher sequence
* number, because the unclean reboot could have happen in the middle of the
* copying process, so the data in P is corrupted. It is also not enough to
* just select the physical eraseblock with lower sequence number, because the
* data there may be old (consider a case if more data was added to P1 after
* the copying). Moreover, the unclean reboot may happen when the erasure of P
* was just started, so it result in unstable P, which is "mostly" OK, but
* still has unstable bits.
* UBI uses the @copy_flag field to indicate that this logical eraseblock is a
* copy. UBI also calculates data CRC when the data is moved and stores it at
* the @data_crc field of the copy (P1). So when UBI needs to pick one physical
* eraseblock of two (P or P1), the @copy_flag of the newer one (P1) is
* examined. If it is cleared, the situation* is simple and the newer one is
* picked. If it is set, the data CRC of the copy (P1) is examined. If the CRC
* checksum is correct, this physical eraseblock is selected (P1). Otherwise
* the older one (P) is selected.
* Note, there is an obsolete @leb_ver field which was used instead of @sqnum
* in the past. But it is not used anymore and we keep it in order to be able
* to deal with old UBI images. It will be removed at some point.
* There are 2 sorts of volumes in UBI: user volumes and internal volumes.
* Internal volumes are not seen from outside and are used for various internal
* UBI purposes. In this implementation there is only one internal volume - the
* layout volume. Internal volumes are the main mechanism of UBI extensions.
* For example, in future one may introduce a journal internal volume. Internal
* volumes have their own reserved range of IDs.
* The @compat field is only used for internal volumes and contains the "degree
* of their compatibility". It is always zero for user volumes. This field
* provides a mechanism to introduce UBI extensions and to be still compatible
* with older UBI binaries. For example, if someone introduced a journal in
* future, he would probably use %UBI_COMPAT_DELETE compatibility for the
* journal volume. And in this case, older UBI binaries, which know nothing
* about the journal volume, would just delete this volume and work perfectly
* fine. This is similar to what Ext2fs does when it is fed by an Ext3fs image
* - it just ignores the Ext3fs journal.
* The @data_crc field contains the CRC checksum of the contents of the logical
* eraseblock if this is a static volume. In case of dynamic volumes, it does
* not contain the CRC checksum as a rule. The only exception is when the
* data of the physical eraseblock was moved by the wear-leveling unit, then
* the wear-leveling unit calculates the data CRC and stores it in the
* @data_crc field. And of course, the @copy_flag is %in this case.
* The @data_size field is used only for static volumes because UBI has to know
* how many bytes of data are stored in this eraseblock. For dynamic volumes,
* this field usually contains zero. The only exception is when the data of the
* physical eraseblock was moved to another physical eraseblock for
* wear-leveling reasons. In this case, UBI calculates CRC checksum of the
* contents and uses both @data_crc and @data_size fields. In this case, the
* @data_size field contains data size.
* The @used_ebs field is used only for static volumes and indicates how many
* eraseblocks the data of the volume takes. For dynamic volumes this field is
* not used and always contains zero.
* The @data_pad is calculated when volumes are created using the alignment
* parameter. So, effectively, the @data_pad field reduces the size of logical
* eraseblocks of this volume. This is very handy when one uses block-oriented
* software (say, cramfs) on top of the UBI volume.
struct ubi_vid_hdr {
__be32 magic;
__u8 version;
__u8 vol_type;
__u8 copy_flag;
__u8 compat;
__be32 vol_id;
__be32 lnum;
__be32 leb_ver; /* obsolete, to be removed, don't use */
__be32 data_size;
__be32 used_ebs;
__be32 data_pad;
__be32 data_crc;
__u8 padding1[4];
__be64 sqnum;
__u8 padding2[12];
__be32 hdr_crc;
} __attribute__ ((packed));
/* Internal UBI volumes count */
* Starting ID of internal volumes. There is reserved room for 4096 internal
* volumes.
/* The layout volume contains the volume table */
#define UBI_LAYOUT_VOLUME_NAME "layout volume"
/* The maximum number of volumes per one UBI device */
#define UBI_MAX_VOLUMES 128
/* The maximum volume name length */
#define UBI_VOL_NAME_MAX 127
/* Size of the volume table record */
#define UBI_VTBL_RECORD_SIZE sizeof(struct ubi_vtbl_record)
/* Size of the volume table record without the ending CRC */
* struct ubi_vtbl_record - a record in the volume table.
* @reserved_pebs: how many physical eraseblocks are reserved for this volume
* @alignment: volume alignment
* @data_pad: how many bytes are unused at the end of the each physical
* eraseblock to satisfy the requested alignment
* @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
* @upd_marker: if volume update was started but not finished
* @name_len: volume name length
* @name: the volume name
* @padding2: reserved, zeroes
* @crc: a CRC32 checksum of the record
* The volume table records are stored in the volume table, which is stored in
* the layout volume. The layout volume consists of 2 logical eraseblock, each
* of which contains a copy of the volume table (i.e., the volume table is
* duplicated). The volume table is an array of &struct ubi_vtbl_record
* objects indexed by the volume ID.
* If the size of the logical eraseblock is large enough to fit
* %UBI_MAX_VOLUMES records, the volume table contains %UBI_MAX_VOLUMES
* records. Otherwise, it contains as many records as it can fit (i.e., size of
* logical eraseblock divided by sizeof(struct ubi_vtbl_record)).
* The @upd_marker flag is used to implement volume update. It is set to %1
* before update and set to %0 after the update. So if the update operation was
* interrupted, UBI knows that the volume is corrupted.
* The @alignment field is specified when the volume is created and cannot be
* later changed. It may be useful, for example, when a block-oriented file
* system works on top of UBI. The @data_pad field is calculated using the
* logical eraseblock size and @alignment. The alignment must be multiple to the
* minimal flash I/O unit. If @alignment is 1, all the available space of
* the physical eraseblocks is used.
* Empty records contain all zeroes and the CRC checksum of those zeroes.
struct ubi_vtbl_record {
__be32 reserved_pebs;
__be32 alignment;
__be32 data_pad;
__u8 vol_type;
__u8 upd_marker;
__be16 name_len;
__u8 name[UBI_VOL_NAME_MAX+1];
__u8 padding2[24];
__be32 crc;
} __attribute__ ((packed));
#endif /* !__UBI_HEADER_H__ */