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authorArtem B. Bityutskiy <dedekind@linutronix.de>2006-06-27 04:22:22 -0400
committerFrank Haverkamp <haver@vnet.ibm.com>2007-04-27 07:23:33 -0400
commit801c135ce73d5df1caf3eca35b66a10824ae0707 (patch)
treeeaf6e7859650557192533b70746479de686c56e1 /include/mtd/ubi-header.h
parentde46c33745f5e2ad594c72f2cf5f490861b16ce1 (diff)
UBI: Unsorted Block Images
UBI (Latin: "where?") manages multiple logical volumes on a single flash device, specifically supporting NAND flash devices. UBI provides a flexible partitioning concept which still allows for wear-levelling across the whole flash device. In a sense, UBI may be compared to the Logical Volume Manager (LVM). Whereas LVM maps logical sector numbers to physical HDD sector numbers, UBI maps logical eraseblocks to physical eraseblocks. More information may be found at http://www.linux-mtd.infradead.org/doc/ubi.html Partitioning/Re-partitioning An UBI volume occupies a certain number of erase blocks. This is limited by a configured maximum volume size, which could also be viewed as the partition size. Each individual UBI volume's size can be changed independently of the other UBI volumes, provided that the sum of all volume sizes doesn't exceed a certain limit. UBI supports dynamic volumes and static volumes. Static volumes are read-only and their contents are protected by CRC check sums. Bad eraseblocks handling UBI transparently handles bad eraseblocks. When a physical eraseblock becomes bad, it is substituted by a good physical eraseblock, and the user does not even notice this. Scrubbing On a NAND flash bit flips can occur on any write operation, sometimes also on read. If bit flips persist on the device, at first they can still be corrected by ECC, but once they accumulate, correction will become impossible. Thus it is best to actively scrub the affected eraseblock, by first copying it to a free eraseblock and then erasing the original. The UBI layer performs this type of scrubbing under the covers, transparently to the UBI volume users. Erase Counts UBI maintains an erase count header per eraseblock. This frees higher-level layers (like file systems) from doing this and allows for centralized erase count management instead. The erase counts are used by the wear-levelling algorithm in the UBI layer. The algorithm itself is exchangeable. Booting from NAND For booting directly from NAND flash the hardware must at least be capable of fetching and executing a small portion of the NAND flash. Some NAND flash controllers have this kind of support. They usually limit the window to a few kilobytes in erase block 0. This "initial program loader" (IPL) must then contain sufficient logic to load and execute the next boot phase. Due to bad eraseblocks, which may be randomly scattered over the flash device, it is problematic to store the "secondary program loader" (SPL) statically. Also, due to bit-flips it may become corrupted over time. UBI allows to solve this problem gracefully by storing the SPL in a small static UBI volume. UBI volumes vs. static partitions UBI volumes are still very similar to static MTD partitions: * both consist of eraseblocks (logical eraseblocks in case of UBI volumes, and physical eraseblocks in case of static partitions; * both support three basic operations - read, write, erase. But UBI volumes have the following advantages over traditional static MTD partitions: * there are no eraseblock wear-leveling constraints in case of UBI volumes, so the user should not care about this; * there are no bit-flips and bad eraseblocks in case of UBI volumes. So, UBI volumes may be considered as flash devices with relaxed restrictions. Where can it be found? Documentation, kernel code and applications can be found in the MTD gits. What are the applications for? The applications help to create binary flash images for two purposes: pfi files (partial flash images) for in-system update of UBI volumes, and plain binary images, with or without OOB data in case of NAND, for a manufacturing step. Furthermore some tools are/and will be created that allow flash content analysis after a system has crashed.. Who did UBI? The original ideas, where UBI is based on, were developed by Andreas Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others were involved too. The implementation of the kernel layer was done by Artem B. Bityutskiy. The user-space applications and tools were written by Oliver Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem. Joern Engel contributed a patch which modifies JFFS2 so that it can be run on a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander Schmidt made some testing work as well as core functionality improvements. Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de> Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
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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 */
55enum {
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 */
70enum {
71 UBI_COMPAT_DELETE = 1,
72 UBI_COMPAT_RO = 2,
73 UBI_COMPAT_PRESERVE = 4,
74 UBI_COMPAT_REJECT = 5
75};
76
77/*
78 * ubi16_t/ubi32_t/ubi64_t - 16, 32, and 64-bit integers used in UBI on-flash
79 * data structures.
80 */
81typedef struct {
82 uint16_t int16;
83} __attribute__ ((packed)) ubi16_t;
84
85typedef struct {
86 uint32_t int32;
87} __attribute__ ((packed)) ubi32_t;
88
89typedef struct {
90 uint64_t int64;
91} __attribute__ ((packed)) ubi64_t;
92
93/*
94 * In this implementation of UBI uses the big-endian format for on-flash
95 * integers. The below are the corresponding conversion macros.
96 */
97#define cpu_to_ubi16(x) ((ubi16_t){__cpu_to_be16(x)})
98#define ubi16_to_cpu(x) ((uint16_t)__be16_to_cpu((x).int16))
99
100#define cpu_to_ubi32(x) ((ubi32_t){__cpu_to_be32(x)})
101#define ubi32_to_cpu(x) ((uint32_t)__be32_to_cpu((x).int32))
102
103#define cpu_to_ubi64(x) ((ubi64_t){__cpu_to_be64(x)})
104#define ubi64_to_cpu(x) ((uint64_t)__be64_to_cpu((x).int64))
105
106/* Sizes of UBI headers */
107#define UBI_EC_HDR_SIZE sizeof(struct ubi_ec_hdr)
108#define UBI_VID_HDR_SIZE sizeof(struct ubi_vid_hdr)
109
110/* Sizes of UBI headers without the ending CRC */
111#define UBI_EC_HDR_SIZE_CRC (UBI_EC_HDR_SIZE - sizeof(ubi32_t))
112#define UBI_VID_HDR_SIZE_CRC (UBI_VID_HDR_SIZE - sizeof(ubi32_t))
113
114/**
115 * struct ubi_ec_hdr - UBI erase counter header.
116 * @magic: erase counter header magic number (%UBI_EC_HDR_MAGIC)
117 * @version: version of UBI implementation which is supposed to accept this
118 * UBI image
119 * @padding1: reserved for future, zeroes
120 * @ec: the erase counter
121 * @vid_hdr_offset: where the VID header starts
122 * @data_offset: where the user data start
123 * @padding2: reserved for future, zeroes
124 * @hdr_crc: erase counter header CRC checksum
125 *
126 * The erase counter header takes 64 bytes and has a plenty of unused space for
127 * future usage. The unused fields are zeroed. The @version field is used to
128 * indicate the version of UBI implementation which is supposed to be able to
129 * work with this UBI image. If @version is greater then the current UBI
130 * version, the image is rejected. This may be useful in future if something
131 * is changed radically. This field is duplicated in the volume identifier
132 * header.
133 *
134 * The @vid_hdr_offset and @data_offset fields contain the offset of the the
135 * volume identifier header and user data, relative to the beginning of the
136 * physical eraseblock. These values have to be the same for all physical
137 * eraseblocks.
138 */
139struct ubi_ec_hdr {
140 ubi32_t magic;
141 uint8_t version;
142 uint8_t padding1[3];
143 ubi64_t ec; /* Warning: the current limit is 31-bit anyway! */
144 ubi32_t vid_hdr_offset;
145 ubi32_t data_offset;
146 uint8_t padding2[36];
147 ubi32_t hdr_crc;
148} __attribute__ ((packed));
149
150/**
151 * struct ubi_vid_hdr - on-flash UBI volume identifier header.
152 * @magic: volume identifier header magic number (%UBI_VID_HDR_MAGIC)
153 * @version: UBI implementation version which is supposed to accept this UBI
154 * image (%UBI_VERSION)
155 * @vol_type: volume type (%UBI_VID_DYNAMIC or %UBI_VID_STATIC)
156 * @copy_flag: if this logical eraseblock was copied from another physical
157 * eraseblock (for wear-leveling reasons)
158 * @compat: compatibility of this volume (%0, %UBI_COMPAT_DELETE,
159 * %UBI_COMPAT_IGNORE, %UBI_COMPAT_PRESERVE, or %UBI_COMPAT_REJECT)
160 * @vol_id: ID of this volume
161 * @lnum: logical eraseblock number
162 * @leb_ver: version of this logical eraseblock (IMPORTANT: obsolete, to be
163 * removed, kept only for not breaking older UBI users)
164 * @data_size: how many bytes of data this logical eraseblock contains
165 * @used_ebs: total number of used logical eraseblocks in this volume
166 * @data_pad: how many bytes at the end of this physical eraseblock are not
167 * used
168 * @data_crc: CRC checksum of the data stored in this logical eraseblock
169 * @padding1: reserved for future, zeroes
170 * @sqnum: sequence number
171 * @padding2: reserved for future, zeroes
172 * @hdr_crc: volume identifier header CRC checksum
173 *
174 * The @sqnum is the value of the global sequence counter at the time when this
175 * VID header was created. The global sequence counter is incremented each time
176 * UBI writes a new VID header to the flash, i.e. when it maps a logical
177 * eraseblock to a new physical eraseblock. The global sequence counter is an
178 * unsigned 64-bit integer and we assume it never overflows. The @sqnum
179 * (sequence number) is used to distinguish between older and newer versions of
180 * logical eraseblocks.
181 *
182 * There are 2 situations when there may be more then one physical eraseblock
183 * corresponding to the same logical eraseblock, i.e., having the same @vol_id
184 * and @lnum values in the volume identifier header. Suppose we have a logical
185 * eraseblock L and it is mapped to the physical eraseblock P.
186 *
187 * 1. Because UBI may erase physical eraseblocks asynchronously, the following
188 * situation is possible: L is asynchronously erased, so P is scheduled for
189 * erasure, then L is written to,i.e. mapped to another physical eraseblock P1,
190 * so P1 is written to, then an unclean reboot happens. Result - there are 2
191 * physical eraseblocks P and P1 corresponding to the same logical eraseblock
192 * L. But P1 has greater sequence number, so UBI picks P1 when it attaches the
193 * flash.
194 *
195 * 2. From time to time UBI moves logical eraseblocks to other physical
196 * eraseblocks for wear-leveling reasons. If, for example, UBI moves L from P
197 * to P1, and an unclean reboot happens before P is physically erased, there
198 * are two physical eraseblocks P and P1 corresponding to L and UBI has to
199 * select one of them when the flash is attached. The @sqnum field says which
200 * PEB is the original (obviously P will have lower @sqnum) and the copy. But
201 * it is not enough to select the physical eraseblock with the higher sequence
202 * number, because the unclean reboot could have happen in the middle of the
203 * copying process, so the data in P is corrupted. It is also not enough to
204 * just select the physical eraseblock with lower sequence number, because the
205 * data there may be old (consider a case if more data was added to P1 after
206 * the copying). Moreover, the unclean reboot may happen when the erasure of P
207 * was just started, so it result in unstable P, which is "mostly" OK, but
208 * still has unstable bits.
209 *
210 * UBI uses the @copy_flag field to indicate that this logical eraseblock is a
211 * copy. UBI also calculates data CRC when the data is moved and stores it at
212 * the @data_crc field of the copy (P1). So when UBI needs to pick one physical
213 * eraseblock of two (P or P1), the @copy_flag of the newer one (P1) is
214 * examined. If it is cleared, the situation* is simple and the newer one is
215 * picked. If it is set, the data CRC of the copy (P1) is examined. If the CRC
216 * checksum is correct, this physical eraseblock is selected (P1). Otherwise
217 * the older one (P) is selected.
218 *
219 * Note, there is an obsolete @leb_ver field which was used instead of @sqnum
220 * in the past. But it is not used anymore and we keep it in order to be able
221 * to deal with old UBI images. It will be removed at some point.
222 *
223 * There are 2 sorts of volumes in UBI: user volumes and internal volumes.
224 * Internal volumes are not seen from outside and are used for various internal
225 * UBI purposes. In this implementation there is only one internal volume - the
226 * layout volume. Internal volumes are the main mechanism of UBI extensions.
227 * For example, in future one may introduce a journal internal volume. Internal
228 * volumes have their own reserved range of IDs.
229 *
230 * The @compat field is only used for internal volumes and contains the "degree
231 * of their compatibility". It is always zero for user volumes. This field
232 * provides a mechanism to introduce UBI extensions and to be still compatible
233 * with older UBI binaries. For example, if someone introduced a journal in
234 * future, he would probably use %UBI_COMPAT_DELETE compatibility for the
235 * journal volume. And in this case, older UBI binaries, which know nothing
236 * about the journal volume, would just delete this volume and work perfectly
237 * fine. This is similar to what Ext2fs does when it is fed by an Ext3fs image
238 * - it just ignores the Ext3fs journal.
239 *
240 * The @data_crc field contains the CRC checksum of the contents of the logical
241 * eraseblock if this is a static volume. In case of dynamic volumes, it does
242 * not contain the CRC checksum as a rule. The only exception is when the
243 * data of the physical eraseblock was moved by the wear-leveling unit, then
244 * the wear-leveling unit calculates the data CRC and stores it in the
245 * @data_crc field. And of course, the @copy_flag is %in this case.
246 *
247 * The @data_size field is used only for static volumes because UBI has to know
248 * how many bytes of data are stored in this eraseblock. For dynamic volumes,
249 * this field usually contains zero. The only exception is when the data of the
250 * physical eraseblock was moved to another physical eraseblock for
251 * wear-leveling reasons. In this case, UBI calculates CRC checksum of the
252 * contents and uses both @data_crc and @data_size fields. In this case, the
253 * @data_size field contains data size.
254 *
255 * The @used_ebs field is used only for static volumes and indicates how many
256 * eraseblocks the data of the volume takes. For dynamic volumes this field is
257 * not used and always contains zero.
258 *
259 * The @data_pad is calculated when volumes are created using the alignment
260 * parameter. So, effectively, the @data_pad field reduces the size of logical
261 * eraseblocks of this volume. This is very handy when one uses block-oriented
262 * software (say, cramfs) on top of the UBI volume.
263 */
264struct ubi_vid_hdr {
265 ubi32_t magic;
266 uint8_t version;
267 uint8_t vol_type;
268 uint8_t copy_flag;
269 uint8_t compat;
270 ubi32_t vol_id;
271 ubi32_t lnum;
272 ubi32_t leb_ver; /* obsolete, to be removed, don't use */
273 ubi32_t data_size;
274 ubi32_t used_ebs;
275 ubi32_t data_pad;
276 ubi32_t data_crc;
277 uint8_t padding1[4];
278 ubi64_t sqnum;
279 uint8_t padding2[12];
280 ubi32_t hdr_crc;
281} __attribute__ ((packed));
282
283/* Internal UBI volumes count */
284#define UBI_INT_VOL_COUNT 1
285
286/*
287 * Starting ID of internal volumes. There is reserved room for 4096 internal
288 * volumes.
289 */
290#define UBI_INTERNAL_VOL_START (0x7FFFFFFF - 4096)
291
292/* The layout volume contains the volume table */
293
294#define UBI_LAYOUT_VOL_ID UBI_INTERNAL_VOL_START
295#define UBI_LAYOUT_VOLUME_EBS 2
296#define UBI_LAYOUT_VOLUME_NAME "layout volume"
297#define UBI_LAYOUT_VOLUME_COMPAT UBI_COMPAT_REJECT
298
299/* The maximum number of volumes per one UBI device */
300#define UBI_MAX_VOLUMES 128
301
302/* The maximum volume name length */
303#define UBI_VOL_NAME_MAX 127
304
305/* Size of the volume table record */
306#define UBI_VTBL_RECORD_SIZE sizeof(struct ubi_vtbl_record)
307
308/* Size of the volume table record without the ending CRC */
309#define UBI_VTBL_RECORD_SIZE_CRC (UBI_VTBL_RECORD_SIZE - sizeof(ubi32_t))
310
311/**
312 * struct ubi_vtbl_record - a record in the volume table.
313 * @reserved_pebs: how many physical eraseblocks are reserved for this volume
314 * @alignment: volume alignment
315 * @data_pad: how many bytes are unused at the end of the each physical
316 * eraseblock to satisfy the requested alignment
317 * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
318 * @upd_marker: if volume update was started but not finished
319 * @name_len: volume name length
320 * @name: the volume name
321 * @padding2: reserved, zeroes
322 * @crc: a CRC32 checksum of the record
323 *
324 * The volume table records are stored in the volume table, which is stored in
325 * the layout volume. The layout volume consists of 2 logical eraseblock, each
326 * of which contains a copy of the volume table (i.e., the volume table is
327 * duplicated). The volume table is an array of &struct ubi_vtbl_record
328 * objects indexed by the volume ID.
329 *
330 * If the size of the logical eraseblock is large enough to fit
331 * %UBI_MAX_VOLUMES records, the volume table contains %UBI_MAX_VOLUMES
332 * records. Otherwise, it contains as many records as it can fit (i.e., size of
333 * logical eraseblock divided by sizeof(struct ubi_vtbl_record)).
334 *
335 * The @upd_marker flag is used to implement volume update. It is set to %1
336 * before update and set to %0 after the update. So if the update operation was
337 * interrupted, UBI knows that the volume is corrupted.
338 *
339 * The @alignment field is specified when the volume is created and cannot be
340 * later changed. It may be useful, for example, when a block-oriented file
341 * system works on top of UBI. The @data_pad field is calculated using the
342 * logical eraseblock size and @alignment. The alignment must be multiple to the
343 * minimal flash I/O unit. If @alignment is 1, all the available space of
344 * the physical eraseblocks is used.
345 *
346 * Empty records contain all zeroes and the CRC checksum of those zeroes.
347 */
348struct ubi_vtbl_record {
349 ubi32_t reserved_pebs;
350 ubi32_t alignment;
351 ubi32_t data_pad;
352 uint8_t vol_type;
353 uint8_t upd_marker;
354 ubi16_t name_len;
355 uint8_t name[UBI_VOL_NAME_MAX+1];
356 uint8_t padding2[24];
357 ubi32_t crc;
358} __attribute__ ((packed));
359
360#endif /* !__UBI_HEADER_H__ */