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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-user.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 * Author: Artem Bityutskiy (Битюцкий Артём)
19 */
20
21#ifndef __UBI_USER_H__
22#define __UBI_USER_H__
23
24/*
25 * UBI volume creation
26 * ~~~~~~~~~~~~~~~~~~~
27 *
28 * UBI volumes are created via the %UBI_IOCMKVOL IOCTL command of UBI character
29 * device. A &struct ubi_mkvol_req object has to be properly filled and a
30 * pointer to it has to be passed to the IOCTL.
31 *
32 * UBI volume deletion
33 * ~~~~~~~~~~~~~~~~~~~
34 *
35 * To delete a volume, the %UBI_IOCRMVOL IOCTL command of the UBI character
36 * device should be used. A pointer to the 32-bit volume ID hast to be passed
37 * to the IOCTL.
38 *
39 * UBI volume re-size
40 * ~~~~~~~~~~~~~~~~~~
41 *
42 * To re-size a volume, the %UBI_IOCRSVOL IOCTL command of the UBI character
43 * device should be used. A &struct ubi_rsvol_req object has to be properly
44 * filled and a pointer to it has to be passed to the IOCTL.
45 *
46 * UBI volume update
47 * ~~~~~~~~~~~~~~~~~
48 *
49 * Volume update should be done via the %UBI_IOCVOLUP IOCTL command of the
50 * corresponding UBI volume character device. A pointer to a 64-bit update
51 * size should be passed to the IOCTL. After then, UBI expects user to write
52 * this number of bytes to the volume character device. The update is finished
53 * when the claimed number of bytes is passed. So, the volume update sequence
54 * is something like:
55 *
56 * fd = open("/dev/my_volume");
57 * ioctl(fd, UBI_IOCVOLUP, &image_size);
58 * write(fd, buf, image_size);
59 * close(fd);
60 */
61
62/*
63 * When a new volume is created, users may either specify the volume number they
64 * want to create or to let UBI automatically assign a volume number using this
65 * constant.
66 */
67#define UBI_VOL_NUM_AUTO (-1)
68
69/* Maximum volume name length */
70#define UBI_MAX_VOLUME_NAME 127
71
72/* IOCTL commands of UBI character devices */
73
74#define UBI_IOC_MAGIC 'o'
75
76/* Create an UBI volume */
77#define UBI_IOCMKVOL _IOW(UBI_IOC_MAGIC, 0, struct ubi_mkvol_req)
78/* Remove an UBI volume */
79#define UBI_IOCRMVOL _IOW(UBI_IOC_MAGIC, 1, int32_t)
80/* Re-size an UBI volume */
81#define UBI_IOCRSVOL _IOW(UBI_IOC_MAGIC, 2, struct ubi_rsvol_req)
82
83/* IOCTL commands of UBI volume character devices */
84
85#define UBI_VOL_IOC_MAGIC 'O'
86
87/* Start UBI volume update */
88#define UBI_IOCVOLUP _IOW(UBI_VOL_IOC_MAGIC, 0, int64_t)
89/* An eraseblock erasure command, used for debugging, disabled by default */
90#define UBI_IOCEBER _IOW(UBI_VOL_IOC_MAGIC, 1, int32_t)
91
92/*
93 * UBI volume type constants.
94 *
95 * @UBI_DYNAMIC_VOLUME: dynamic volume
96 * @UBI_STATIC_VOLUME: static volume
97 */
98enum {
99 UBI_DYNAMIC_VOLUME = 3,
100 UBI_STATIC_VOLUME = 4
101};
102
103/**
104 * struct ubi_mkvol_req - volume description data structure used in
105 * volume creation requests.
106 * @vol_id: volume number
107 * @alignment: volume alignment
108 * @bytes: volume size in bytes
109 * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
110 * @padding1: reserved for future, not used
111 * @name_len: volume name length
112 * @padding2: reserved for future, not used
113 * @name: volume name
114 *
115 * This structure is used by userspace programs when creating new volumes. The
116 * @used_bytes field is only necessary when creating static volumes.
117 *
118 * The @alignment field specifies the required alignment of the volume logical
119 * eraseblock. This means, that the size of logical eraseblocks will be aligned
120 * to this number, i.e.,
121 * (UBI device logical eraseblock size) mod (@alignment) = 0.
122 *
123 * To put it differently, the logical eraseblock of this volume may be slightly
124 * shortened in order to make it properly aligned. The alignment has to be
125 * multiple of the flash minimal input/output unit, or %1 to utilize the entire
126 * available space of logical eraseblocks.
127 *
128 * The @alignment field may be useful, for example, when one wants to maintain
129 * a block device on top of an UBI volume. In this case, it is desirable to fit
130 * an integer number of blocks in logical eraseblocks of this UBI volume. With
131 * alignment it is possible to update this volume using plane UBI volume image
132 * BLOBs, without caring about how to properly align them.
133 */
134struct ubi_mkvol_req {
135 int32_t vol_id;
136 int32_t alignment;
137 int64_t bytes;
138 int8_t vol_type;
139 int8_t padding1;
140 int16_t name_len;
141 int8_t padding2[4];
142 char name[UBI_MAX_VOLUME_NAME+1];
143} __attribute__ ((packed));
144
145/**
146 * struct ubi_rsvol_req - a data structure used in volume re-size requests.
147 * @vol_id: ID of the volume to re-size
148 * @bytes: new size of the volume in bytes
149 *
150 * Re-sizing is possible for both dynamic and static volumes. But while dynamic
151 * volumes may be re-sized arbitrarily, static volumes cannot be made to be
152 * smaller then the number of bytes they bear. To arbitrarily shrink a static
153 * volume, it must be wiped out first (by means of volume update operation with
154 * zero number of bytes).
155 */
156struct ubi_rsvol_req {
157 int64_t bytes;
158 int32_t vol_id;
159} __attribute__ ((packed));
160
161#endif /* __UBI_USER_H__ */