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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 /drivers/mtd/ubi/scan.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_SCAN_H__
22#define __UBI_SCAN_H__
23
24/* The erase counter value for this physical eraseblock is unknown */
25#define UBI_SCAN_UNKNOWN_EC (-1)
26
27/**
28 * struct ubi_scan_leb - scanning information about a physical eraseblock.
29 * @ec: erase counter (%UBI_SCAN_UNKNOWN_EC if it is unknown)
30 * @pnum: physical eraseblock number
31 * @lnum: logical eraseblock number
32 * @scrub: if this physical eraseblock needs scrubbing
33 * @sqnum: sequence number
34 * @u: unions RB-tree or @list links
35 * @u.rb: link in the per-volume RB-tree of &struct ubi_scan_leb objects
36 * @u.list: link in one of the eraseblock lists
37 * @leb_ver: logical eraseblock version (obsolete)
38 *
39 * One object of this type is allocated for each physical eraseblock during
40 * scanning.
41 */
42struct ubi_scan_leb {
43 int ec;
44 int pnum;
45 int lnum;
46 int scrub;
47 unsigned long long sqnum;
48 union {
49 struct rb_node rb;
50 struct list_head list;
51 } u;
52 uint32_t leb_ver;
53};
54
55/**
56 * struct ubi_scan_volume - scanning information about a volume.
57 * @vol_id: volume ID
58 * @highest_lnum: highest logical eraseblock number in this volume
59 * @leb_count: number of logical eraseblocks in this volume
60 * @vol_type: volume type
61 * @used_ebs: number of used logical eraseblocks in this volume (only for
62 * static volumes)
63 * @last_data_size: amount of data in the last logical eraseblock of this
64 * volume (always equivalent to the usable logical eraseblock size in case of
65 * dynamic volumes)
66 * @data_pad: how many bytes at the end of logical eraseblocks of this volume
67 * are not used (due to volume alignment)
68 * @compat: compatibility flags of this volume
69 * @rb: link in the volume RB-tree
70 * @root: root of the RB-tree containing all the eraseblock belonging to this
71 * volume (&struct ubi_scan_leb objects)
72 *
73 * One object of this type is allocated for each volume during scanning.
74 */
75struct ubi_scan_volume {
76 int vol_id;
77 int highest_lnum;
78 int leb_count;
79 int vol_type;
80 int used_ebs;
81 int last_data_size;
82 int data_pad;
83 int compat;
84 struct rb_node rb;
85 struct rb_root root;
86};
87
88/**
89 * struct ubi_scan_info - UBI scanning information.
90 * @volumes: root of the volume RB-tree
91 * @corr: list of corrupted physical eraseblocks
92 * @free: list of free physical eraseblocks
93 * @erase: list of physical eraseblocks which have to be erased
94 * @alien: list of physical eraseblocks which should not be used by UBI (e.g.,
95 * @bad_peb_count: count of bad physical eraseblocks
96 * those belonging to "preserve"-compatible internal volumes)
97 * @vols_found: number of volumes found during scanning
98 * @highest_vol_id: highest volume ID
99 * @alien_peb_count: count of physical eraseblocks in the @alien list
100 * @is_empty: flag indicating whether the MTD device is empty or not
101 * @min_ec: lowest erase counter value
102 * @max_ec: highest erase counter value
103 * @max_sqnum: highest sequence number value
104 * @mean_ec: mean erase counter value
105 * @ec_sum: a temporary variable used when calculating @mean_ec
106 * @ec_count: a temporary variable used when calculating @mean_ec
107 *
108 * This data structure contains the result of scanning and may be used by other
109 * UBI units to build final UBI data structures, further error-recovery and so
110 * on.
111 */
112struct ubi_scan_info {
113 struct rb_root volumes;
114 struct list_head corr;
115 struct list_head free;
116 struct list_head erase;
117 struct list_head alien;
118 int bad_peb_count;
119 int vols_found;
120 int highest_vol_id;
121 int alien_peb_count;
122 int is_empty;
123 int min_ec;
124 int max_ec;
125 unsigned long long max_sqnum;
126 int mean_ec;
127 int ec_sum;
128 int ec_count;
129};
130
131struct ubi_device;
132struct ubi_vid_hdr;
133
134/*
135 * ubi_scan_move_to_list - move a physical eraseblock from the volume tree to a
136 * list.
137 *
138 * @sv: volume scanning information
139 * @seb: scanning eraseblock infprmation
140 * @list: the list to move to
141 */
142static inline void ubi_scan_move_to_list(struct ubi_scan_volume *sv,
143 struct ubi_scan_leb *seb,
144 struct list_head *list)
145{
146 rb_erase(&seb->u.rb, &sv->root);
147 list_add_tail(&seb->u.list, list);
148}
149
150int ubi_scan_add_to_list(struct ubi_scan_info *si, int pnum, int ec,
151 struct list_head *list);
152int ubi_scan_add_used(const struct ubi_device *ubi, struct ubi_scan_info *si,
153 int pnum, int ec, const struct ubi_vid_hdr *vid_hdr,
154 int bitflips);
155struct ubi_scan_volume *ubi_scan_find_sv(const struct ubi_scan_info *si,
156 int vol_id);
157struct ubi_scan_leb *ubi_scan_find_seb(const struct ubi_scan_volume *sv,
158 int lnum);
159void ubi_scan_rm_volume(struct ubi_scan_info *si, struct ubi_scan_volume *sv);
160struct ubi_scan_leb *ubi_scan_get_free_peb(const struct ubi_device *ubi,
161 struct ubi_scan_info *si);
162int ubi_scan_erase_peb(const struct ubi_device *ubi,
163 const struct ubi_scan_info *si, int pnum, int ec);
164struct ubi_scan_info *ubi_scan(struct ubi_device *ubi);
165void ubi_scan_destroy_si(struct ubi_scan_info *si);
166
167#endif /* !__UBI_SCAN_H__ */