Message-Id: <20070217165434.5845.54262.sendpatchset@localhost.localdomain>
Date:	Sat, 17 Feb 2007 18:54:34 +0200
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Artem Bityutskiy <dedekind@...radead.org>,
	Frank Haverkamp <haver@...t.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Woodhouse <dwmw2@...radead.org>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>
Subject: [PATCH 02/44 take 2] [UBI] on-flash data structures header

diff -auNrp tmp-from/include/mtd/ubi-header.h tmp-to/include/mtd/ubi-header.h
--- tmp-from/include/mtd/ubi-header.h	1970-01-01 02:00:00.000000000 +0200
+++ tmp-to/include/mtd/ubi-header.h	2007-02-17 18:07:26.000000000 +0200
@@ -0,0 +1,337 @@
+/*
+ * 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
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ * 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 B. Bityutskiy
+ *          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.
+ */
+
+#ifndef __UBI_HEADER_H__
+#define __UBI_HEADER_H__
+
+#include <asm/byteorder.h>
+
+/* The version of this UBI implementation */
+#define UBI_VERSION 1
+
+/* The highest erase counter value supported by this implementation of UBI */
+#define UBI_MAX_ERASECOUNTER 0x7FFFFFFF
+
+/* The initial CRC32 value used when calculating CRC checksums */
+#define UBI_CRC32_INIT 0xFFFFFFFFU
+
+/*
+ * Magic numbers of the UBI headers.
+ *
+ * @UBI_EC_HDR_MAGIC: erase counter header magic number (ASCII "UBI#")
+ * @UBI_VID_HDR_MAGIC: volume identifier header magic number (ASCII "UBI!")
+ */
+enum {
+	UBI_EC_HDR_MAGIC  = 0x55424923,
+	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 {
+	UBI_VID_DYNAMIC = 1,
+	UBI_VID_STATIC  = 2
+};
+
+/*
+ * 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 {
+	UBI_COMPAT_DELETE   = 1,
+	UBI_COMPAT_RO       = 2,
+	UBI_COMPAT_PRESERVE = 4,
+	UBI_COMPAT_REJECT   = 5
+};
+
+/*
+ * ubi16_t/ubi32_t/ubi64_t - 16, 32, and 64-bit integers used in UBI on-flash
+ * data structures.
+ */
+typedef struct {
+	uint16_t int16;
+} __attribute__ ((packed)) ubi16_t;
+
+typedef struct {
+	uint32_t int32;
+} __attribute__ ((packed)) ubi32_t;
+
+typedef struct {
+	uint64_t int64;
+} __attribute__ ((packed)) ubi64_t;
+
+/*
+ * In this implementation of UBI uses the big-endian format for on-flash
+ * integers. The below are the corresponding conversion macros.
+ */
+#define cpu_to_ubi16(x) ((ubi16_t){__cpu_to_be16(x)})
+#define ubi16_to_cpu(x) ((uint16_t)__be16_to_cpu((x).int16))
+
+#define cpu_to_ubi32(x) ((ubi32_t){__cpu_to_be32(x)})
+#define ubi32_to_cpu(x) ((uint32_t)__be32_to_cpu((x).int32))
+
+#define cpu_to_ubi64(x) ((ubi64_t){__cpu_to_be64(x)})
+#define ubi64_to_cpu(x) ((uint64_t)__be64_to_cpu((x).int64))
+
+/* 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(ubi32_t))
+#define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(ubi32_t))
+
+/**
+ * struct ubi_ec_hdr - UBI erase counter header.
+ *
+ * @magic: the erase counter header magic number (%UBI_EC_HDR_MAGIC)
+ * @version: the version of UBI implementation which is supposed to accept this
+ * UBI image (%UBI_VERSION)
+ * @padding1: reserved for future, zeroes
+ * @ec: the erase counter
+ * @vid_hdr_offset: where the VID header starts
+ * @data_offset: where the user data starts
+ * @padding2: reserved for future, zeroes
+ * @hdr_crc: the 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
+ * eraseblock. These values have to be the same for all eraseblocks.
+ */
+struct ubi_ec_hdr {
+	ubi32_t magic;
+	uint8_t version;
+	uint8_t padding1[3];
+	ubi64_t ec; /* Warning: the current limit is 31-bit anyway! */
+	ubi32_t vid_hdr_offset;
+	ubi32_t data_offset;
+	uint8_t padding2[36];
+	ubi32_t 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: a flag indicating if this physical eraseblock was created by
+ * means of copying an original physical eraseblock to ensure wear-leveling.
+ * @compat: compatibility of this volume (%UBI_COMPAT_DELETE,
+ * %UBI_COMPAT_IGNORE, %UBI_COMPAT_PRESERVE, or %UBI_COMPAT_REJECT)
+ * @vol_id: ID of this volume
+ * @lnum: logical eraseblock number
+ * @leb_ver: eraseblock copy number
+ * @data_size: how many bytes of data this eraseblock contains
+ * @used_ebs: total number of used logical eraseblocks in this volume
+ * @data_pad: how many bytes at the end of this eraseblock are not used
+ * @data_crc: CRC checksum of the data stored in this eraseblock
+ * @padding1: reserved for future, zeroes
+ * @hdr_crc: volume identifier header CRC checksum
+ *
+ * The @leb_ver and the @copy_flag fields are used to distinguish between older
+ * and newer copies of the logical eraseblock, as well as to guarantee
+ * robustness against unclean reboots. As UBI erases logical eraseblocks
+ * asynchronously, in background, it has to distinguish between older and newer
+ * copies of logical eraseblocks. This is done using the @version field. On the
+ * other hand, when UBI moves data of an eraseblock, its version is also
+ * increased and the @copy_flag is set to 1. Additionally, when moving data of
+ * eraseblocks, UBI calculates data CRC and stores it in the @data_crc field,
+ * even for dynamic volumes.
+ *
+ * Thus, if there are 2 physical eraseblocks belonging to the logical
+ * eraseblock (same volume ID and logical eraseblock number), UBI uses the
+ * following algorithm to pick one of them. It first picks the one with larger
+ * version (say, A). If @copy_flag is not set, then A is picked. If @copy_flag
+ * is set, UBI checks the CRC of data of this physical eraseblock (@data_crc).
+ * This is needed to ensure that the copying was finished. If the CRC is all
+ * right, A is picked. If not, the older physical eraseblock is picked.
+ *
+ * Note, the @leb_ver field may overflow. Thus, if you have 2 versions X and Y,
+ * then X > Y if abs(X-Y) < 0x7FFFFFFF, otherwise X < Y.
+ *
+ * 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 somewhat 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 {
+	ubi32_t magic;
+	uint8_t version;
+	uint8_t vol_type;
+	uint8_t copy_flag;
+	uint8_t compat;
+	ubi32_t vol_id;
+	ubi32_t lnum;
+	ubi32_t leb_ver;
+	ubi32_t data_size;
+	ubi32_t used_ebs;
+	ubi32_t data_pad;
+	ubi32_t data_crc;
+	uint8_t padding1[24];
+	ubi32_t hdr_crc;
+} __attribute__ ((packed));
+
+/* Count of internal UBI volumes */
+#define UBI_INT_VOL_COUNT 1
+
+/*
+ * IDs of internal volumes start from this digit. There is a reserved room for
+ * 4096 internal volumes.
+ */
+#define UBI_INTERNAL_VOL_START (0x7FFFFFFF - 4096)
+
+/*
+ * IDs of internal UBI volumes.
+ *
+ * %UBI_LAYOUT_VOL_ID: layout volume ID
+ */
+enum {
+	UBI_LAYOUT_VOL_ID = UBI_INTERNAL_VOL_START,
+};
+
+#define UBI_LAYOUT_VOLUME_EBS    2
+#define UBI_LAYOUT_VOLUME_NAME   "The layout volume"
+#define UBI_LAYOUT_VOLUME_COMPAT UBI_COMPAT_REJECT
+
+/* 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_vol_tbl_record)
+
+/* Size of the volume table record without the ending CRC */
+#define UBI_VTBL_RECORD_SIZE_CRC (UBI_VTBL_RECORD_SIZE - sizeof(ubi32_t))
+
+/**
+ * struct ubi_vol_tbl_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 eraseblock to
+ * satisfy the requested alignment
+ * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
+ * @upd_marker: the update marker flag
+ * @name_len: the volume name length
+ * @name: the volume name
+ * @padding2: reserved, zeroes
+ * @crc: a CRC32 checksum of the record
+ *
+ * The layout volume consists of 2 logical eraseblock, each of which contains
+ * the volume table (i.e., the volume table is duplicated). The volume table is
+ * an array of &struct ubi_vol_tbl_record objects indexed by the volume ID.
+ *
+ * If the size of the logical eraseblock is large enough to fit
+ * %UBI_MAX_VOLUMES, 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_vol_tbl_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.
+ *
+ * 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
+ * eraseblocks is used.
+ *
+ * Empty records contain all zeroes and the CRC checksum of those zeroes.
+ */
+struct ubi_vol_tbl_record {
+	ubi32_t reserved_pebs;
+	ubi32_t alignment;
+	ubi32_t data_pad;
+	uint8_t vol_type;
+	uint8_t upd_marker;
+	ubi16_t name_len;
+	uint8_t name[UBI_VOL_NAME_MAX+1];
+	uint8_t padding2[24];
+	ubi32_t crc;
+} __attribute__ ((packed));
+
+#endif /* !__UBI_HEADER_H__ */
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