379 lines
16 KiB
C
379 lines
16 KiB
C
/*
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* Copyright (c) International Business Machines Corp., 2006
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Authors: Artem Bityutskiy (Битюцкий Артём)
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* Thomas Gleixner
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* Frank Haverkamp
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* Oliver Lohmann
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* Andreas Arnez
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*/
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/*
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* This file defines the layout of UBI headers and all the other UBI on-flash
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* data structures.
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*/
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#ifndef __UBI_MEDIA_H__
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#define __UBI_MEDIA_H__
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#include <asm/byteorder.h>
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/* The version of UBI images supported by this implementation */
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#define UBI_VERSION 1
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/* The highest erase counter value supported by this implementation */
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#define UBI_MAX_ERASECOUNTER 0x7FFFFFFF
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/* The initial CRC32 value used when calculating CRC checksums */
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#define UBI_CRC32_INIT 0xFFFFFFFFU
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/* Erase counter header magic number (ASCII "UBI#") */
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#define UBI_EC_HDR_MAGIC 0x55424923
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/* Volume identifier header magic number (ASCII "UBI!") */
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#define UBI_VID_HDR_MAGIC 0x55424921
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/*
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* Volume type constants used in the volume identifier header.
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*
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* @UBI_VID_DYNAMIC: dynamic volume
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* @UBI_VID_STATIC: static volume
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*/
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enum {
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UBI_VID_DYNAMIC = 1,
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UBI_VID_STATIC = 2
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};
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/*
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* Volume flags used in the volume table record.
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*
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* @UBI_VTBL_AUTORESIZE_FLG: auto-resize this volume
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*
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* %UBI_VTBL_AUTORESIZE_FLG flag can be set only for one volume in the volume
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* table. UBI automatically re-sizes the volume which has this flag and makes
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* the volume to be of largest possible size. This means that if after the
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* initialization UBI finds out that there are available physical eraseblocks
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* present on the device, it automatically appends all of them to the volume
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* (the physical eraseblocks reserved for bad eraseblocks handling and other
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* reserved physical eraseblocks are not taken). So, if there is a volume with
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* the %UBI_VTBL_AUTORESIZE_FLG flag set, the amount of available logical
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* eraseblocks will be zero after UBI is loaded, because all of them will be
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* reserved for this volume. Note, the %UBI_VTBL_AUTORESIZE_FLG bit is cleared
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* after the volume had been initialized.
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*
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* The auto-resize feature is useful for device production purposes. For
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* example, different NAND flash chips may have different amount of initial bad
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* eraseblocks, depending of particular chip instance. Manufacturers of NAND
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* chips usually guarantee that the amount of initial bad eraseblocks does not
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* exceed certain percent, e.g. 2%. When one creates an UBI image which will be
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* flashed to the end devices in production, he does not know the exact amount
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* of good physical eraseblocks the NAND chip on the device will have, but this
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* number is required to calculate the volume sized and put them to the volume
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* table of the UBI image. In this case, one of the volumes (e.g., the one
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* which will store the root file system) is marked as "auto-resizable", and
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* UBI will adjust its size on the first boot if needed.
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*
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* Note, first UBI reserves some amount of physical eraseblocks for bad
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* eraseblock handling, and then re-sizes the volume, not vice-versa. This
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* means that the pool of reserved physical eraseblocks will always be present.
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*/
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enum {
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UBI_VTBL_AUTORESIZE_FLG = 0x01,
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};
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/*
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* Compatibility constants used by internal volumes.
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*
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* @UBI_COMPAT_DELETE: delete this internal volume before anything is written
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* to the flash
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* @UBI_COMPAT_RO: attach this device in read-only mode
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* @UBI_COMPAT_PRESERVE: preserve this internal volume - do not touch its
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* physical eraseblocks, don't allow the wear-leveling
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* sub-system to move them
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* @UBI_COMPAT_REJECT: reject this UBI image
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*/
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enum {
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UBI_COMPAT_DELETE = 1,
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UBI_COMPAT_RO = 2,
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UBI_COMPAT_PRESERVE = 4,
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UBI_COMPAT_REJECT = 5
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};
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/* Sizes of UBI headers */
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#define UBI_EC_HDR_SIZE sizeof(struct ubi_ec_hdr)
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#define UBI_VID_HDR_SIZE sizeof(struct ubi_vid_hdr)
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/* Sizes of UBI headers without the ending CRC */
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#define UBI_EC_HDR_SIZE_CRC (UBI_EC_HDR_SIZE - sizeof(__be32))
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#define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(__be32))
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/**
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* struct ubi_ec_hdr - UBI erase counter header.
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* @magic: erase counter header magic number (%UBI_EC_HDR_MAGIC)
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* @version: version of UBI implementation which is supposed to accept this
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* UBI image
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* @padding1: reserved for future, zeroes
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* @ec: the erase counter
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* @vid_hdr_offset: where the VID header starts
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* @data_offset: where the user data start
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* @image_seq: image sequence number
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* @padding2: reserved for future, zeroes
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* @hdr_crc: erase counter header CRC checksum
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*
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* The erase counter header takes 64 bytes and has a plenty of unused space for
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* future usage. The unused fields are zeroed. The @version field is used to
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* indicate the version of UBI implementation which is supposed to be able to
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* work with this UBI image. If @version is greater than the current UBI
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* version, the image is rejected. This may be useful in future if something
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* is changed radically. This field is duplicated in the volume identifier
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* header.
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*
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* The @vid_hdr_offset and @data_offset fields contain the offset of the the
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* volume identifier header and user data, relative to the beginning of the
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* physical eraseblock. These values have to be the same for all physical
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* eraseblocks.
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*
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* The @image_seq field is used to validate a UBI image that has been prepared
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* for a UBI device. The @image_seq value can be any value, but it must be the
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* same on all eraseblocks. UBI will ensure that all new erase counter headers
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* also contain this value, and will check the value when scanning at start-up.
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* One way to make use of @image_seq is to increase its value by one every time
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* an image is flashed over an existing image, then, if the flashing does not
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* complete, UBI will detect the error when scanning.
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*/
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struct ubi_ec_hdr {
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__be32 magic;
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__u8 version;
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__u8 padding1[3];
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__be64 ec; /* Warning: the current limit is 31-bit anyway! */
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__be32 vid_hdr_offset;
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__be32 data_offset;
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__be32 image_seq;
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__u8 padding2[32];
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__be32 hdr_crc;
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} __attribute__ ((packed));
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/**
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* struct ubi_vid_hdr - on-flash UBI volume identifier header.
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* @magic: volume identifier header magic number (%UBI_VID_HDR_MAGIC)
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* @version: UBI implementation version which is supposed to accept this UBI
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* image (%UBI_VERSION)
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* @vol_type: volume type (%UBI_VID_DYNAMIC or %UBI_VID_STATIC)
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* @copy_flag: if this logical eraseblock was copied from another physical
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* eraseblock (for wear-leveling reasons)
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* @compat: compatibility of this volume (%0, %UBI_COMPAT_DELETE,
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* %UBI_COMPAT_IGNORE, %UBI_COMPAT_PRESERVE, or %UBI_COMPAT_REJECT)
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* @vol_id: ID of this volume
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* @lnum: logical eraseblock number
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* @padding1: reserved for future, zeroes
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* @data_size: how many bytes of data this logical eraseblock contains
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* @used_ebs: total number of used logical eraseblocks in this volume
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* @data_pad: how many bytes at the end of this physical eraseblock are not
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* used
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* @data_crc: CRC checksum of the data stored in this logical eraseblock
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* @padding2: reserved for future, zeroes
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* @sqnum: sequence number
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* @padding3: reserved for future, zeroes
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* @hdr_crc: volume identifier header CRC checksum
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*
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* The @sqnum is the value of the global sequence counter at the time when this
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* VID header was created. The global sequence counter is incremented each time
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* UBI writes a new VID header to the flash, i.e. when it maps a logical
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* eraseblock to a new physical eraseblock. The global sequence counter is an
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* unsigned 64-bit integer and we assume it never overflows. The @sqnum
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* (sequence number) is used to distinguish between older and newer versions of
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* logical eraseblocks.
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*
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* There are 2 situations when there may be more than one physical eraseblock
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* corresponding to the same logical eraseblock, i.e., having the same @vol_id
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* and @lnum values in the volume identifier header. Suppose we have a logical
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* eraseblock L and it is mapped to the physical eraseblock P.
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*
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* 1. Because UBI may erase physical eraseblocks asynchronously, the following
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* situation is possible: L is asynchronously erased, so P is scheduled for
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* erasure, then L is written to,i.e. mapped to another physical eraseblock P1,
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* so P1 is written to, then an unclean reboot happens. Result - there are 2
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* physical eraseblocks P and P1 corresponding to the same logical eraseblock
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* L. But P1 has greater sequence number, so UBI picks P1 when it attaches the
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* flash.
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*
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* 2. From time to time UBI moves logical eraseblocks to other physical
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* eraseblocks for wear-leveling reasons. If, for example, UBI moves L from P
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* to P1, and an unclean reboot happens before P is physically erased, there
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* are two physical eraseblocks P and P1 corresponding to L and UBI has to
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* select one of them when the flash is attached. The @sqnum field says which
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* PEB is the original (obviously P will have lower @sqnum) and the copy. But
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* it is not enough to select the physical eraseblock with the higher sequence
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* number, because the unclean reboot could have happen in the middle of the
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* copying process, so the data in P is corrupted. It is also not enough to
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* just select the physical eraseblock with lower sequence number, because the
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* data there may be old (consider a case if more data was added to P1 after
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* the copying). Moreover, the unclean reboot may happen when the erasure of P
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* was just started, so it result in unstable P, which is "mostly" OK, but
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* still has unstable bits.
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*
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* UBI uses the @copy_flag field to indicate that this logical eraseblock is a
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* copy. UBI also calculates data CRC when the data is moved and stores it at
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* the @data_crc field of the copy (P1). So when UBI needs to pick one physical
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* eraseblock of two (P or P1), the @copy_flag of the newer one (P1) is
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* examined. If it is cleared, the situation* is simple and the newer one is
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* picked. If it is set, the data CRC of the copy (P1) is examined. If the CRC
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* checksum is correct, this physical eraseblock is selected (P1). Otherwise
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* the older one (P) is selected.
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*
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* There are 2 sorts of volumes in UBI: user volumes and internal volumes.
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* Internal volumes are not seen from outside and are used for various internal
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* UBI purposes. In this implementation there is only one internal volume - the
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* layout volume. Internal volumes are the main mechanism of UBI extensions.
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* For example, in future one may introduce a journal internal volume. Internal
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* volumes have their own reserved range of IDs.
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*
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* The @compat field is only used for internal volumes and contains the "degree
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* of their compatibility". It is always zero for user volumes. This field
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* provides a mechanism to introduce UBI extensions and to be still compatible
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* with older UBI binaries. For example, if someone introduced a journal in
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* future, he would probably use %UBI_COMPAT_DELETE compatibility for the
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* journal volume. And in this case, older UBI binaries, which know nothing
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* about the journal volume, would just delete this volume and work perfectly
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* fine. This is similar to what Ext2fs does when it is fed by an Ext3fs image
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* - it just ignores the Ext3fs journal.
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*
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* The @data_crc field contains the CRC checksum of the contents of the logical
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* eraseblock if this is a static volume. In case of dynamic volumes, it does
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* not contain the CRC checksum as a rule. The only exception is when the
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* data of the physical eraseblock was moved by the wear-leveling sub-system,
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* then the wear-leveling sub-system calculates the data CRC and stores it in
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* the @data_crc field. And of course, the @copy_flag is %in this case.
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*
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* The @data_size field is used only for static volumes because UBI has to know
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* how many bytes of data are stored in this eraseblock. For dynamic volumes,
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* this field usually contains zero. The only exception is when the data of the
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* physical eraseblock was moved to another physical eraseblock for
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* wear-leveling reasons. In this case, UBI calculates CRC checksum of the
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* contents and uses both @data_crc and @data_size fields. In this case, the
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* @data_size field contains data size.
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*
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* The @used_ebs field is used only for static volumes and indicates how many
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* eraseblocks the data of the volume takes. For dynamic volumes this field is
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* not used and always contains zero.
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*
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* The @data_pad is calculated when volumes are created using the alignment
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* parameter. So, effectively, the @data_pad field reduces the size of logical
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* eraseblocks of this volume. This is very handy when one uses block-oriented
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* software (say, cramfs) on top of the UBI volume.
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*/
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struct ubi_vid_hdr {
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__be32 magic;
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__u8 version;
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__u8 vol_type;
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__u8 copy_flag;
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__u8 compat;
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__be32 vol_id;
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__be32 lnum;
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__u8 padding1[4];
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__be32 data_size;
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__be32 used_ebs;
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__be32 data_pad;
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__be32 data_crc;
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__u8 padding2[4];
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__be64 sqnum;
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__u8 padding3[12];
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__be32 hdr_crc;
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} __attribute__ ((packed));
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/* Internal UBI volumes count */
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#define UBI_INT_VOL_COUNT 1
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/*
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* Starting ID of internal volumes. There is reserved room for 4096 internal
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* volumes.
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*/
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#define UBI_INTERNAL_VOL_START (0x7FFFFFFF - 4096)
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/* The layout volume contains the volume table */
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#define UBI_LAYOUT_VOLUME_ID UBI_INTERNAL_VOL_START
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#define UBI_LAYOUT_VOLUME_TYPE UBI_VID_DYNAMIC
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#define UBI_LAYOUT_VOLUME_ALIGN 1
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#define UBI_LAYOUT_VOLUME_EBS 2
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#define UBI_LAYOUT_VOLUME_NAME "layout volume"
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#define UBI_LAYOUT_VOLUME_COMPAT UBI_COMPAT_REJECT
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/* The maximum number of volumes per one UBI device */
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#define UBI_MAX_VOLUMES 128
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/* The maximum volume name length */
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#define UBI_VOL_NAME_MAX 127
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/* Size of the volume table record */
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#define UBI_VTBL_RECORD_SIZE sizeof(struct ubi_vtbl_record)
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/* Size of the volume table record without the ending CRC */
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#define UBI_VTBL_RECORD_SIZE_CRC (UBI_VTBL_RECORD_SIZE - sizeof(__be32))
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/**
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* struct ubi_vtbl_record - a record in the volume table.
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* @reserved_pebs: how many physical eraseblocks are reserved for this volume
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* @alignment: volume alignment
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* @data_pad: how many bytes are unused at the end of the each physical
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* eraseblock to satisfy the requested alignment
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* @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
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* @upd_marker: if volume update was started but not finished
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* @name_len: volume name length
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* @name: the volume name
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* @flags: volume flags (%UBI_VTBL_AUTORESIZE_FLG)
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* @padding: reserved, zeroes
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* @crc: a CRC32 checksum of the record
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*
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* The volume table records are stored in the volume table, which is stored in
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* the layout volume. The layout volume consists of 2 logical eraseblock, each
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* of which contains a copy of the volume table (i.e., the volume table is
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* duplicated). The volume table is an array of &struct ubi_vtbl_record
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* objects indexed by the volume ID.
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*
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* If the size of the logical eraseblock is large enough to fit
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* %UBI_MAX_VOLUMES records, the volume table contains %UBI_MAX_VOLUMES
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* records. Otherwise, it contains as many records as it can fit (i.e., size of
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* logical eraseblock divided by sizeof(struct ubi_vtbl_record)).
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*
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* The @upd_marker flag is used to implement volume update. It is set to %1
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* before update and set to %0 after the update. So if the update operation was
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* interrupted, UBI knows that the volume is corrupted.
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*
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* The @alignment field is specified when the volume is created and cannot be
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* later changed. It may be useful, for example, when a block-oriented file
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* system works on top of UBI. The @data_pad field is calculated using the
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* logical eraseblock size and @alignment. The alignment must be multiple to the
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* minimal flash I/O unit. If @alignment is 1, all the available space of
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* the physical eraseblocks is used.
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*
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* Empty records contain all zeroes and the CRC checksum of those zeroes.
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*/
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struct ubi_vtbl_record {
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__be32 reserved_pebs;
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__be32 alignment;
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__be32 data_pad;
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__u8 vol_type;
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__u8 upd_marker;
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__be16 name_len;
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__u8 name[UBI_VOL_NAME_MAX+1];
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__u8 flags;
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__u8 padding[23];
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__be32 crc;
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} __attribute__ ((packed));
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#endif /* !__UBI_MEDIA_H__ */
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