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![Artem B. Bityutskiy](/assets/img/avatar_default.png)
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>
161 lines
4.6 KiB
C
161 lines
4.6 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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* Author: Artem Bityutskiy (Битюцкий Артём)
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*/
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#ifndef __UBI_DEBUG_H__
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#define __UBI_DEBUG_H__
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#ifdef CONFIG_MTD_UBI_DEBUG
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#include <linux/random.h>
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#define ubi_assert(expr) BUG_ON(!(expr))
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#define dbg_err(fmt, ...) ubi_err(fmt, ##__VA_ARGS__)
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#else
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#define ubi_assert(expr) ({})
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#define dbg_err(fmt, ...) ({})
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_DISABLE_BGT
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#define DBG_DISABLE_BGT 1
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#else
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#define DBG_DISABLE_BGT 0
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_MSG
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/* Generic debugging message */
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#define dbg_msg(fmt, ...) \
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printk(KERN_DEBUG "UBI DBG: %s: " fmt "\n", __FUNCTION__, ##__VA_ARGS__)
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#define ubi_dbg_dump_stack() dump_stack()
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struct ubi_ec_hdr;
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struct ubi_vid_hdr;
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struct ubi_volume;
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struct ubi_vtbl_record;
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struct ubi_scan_volume;
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struct ubi_scan_leb;
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struct ubi_mkvol_req;
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void ubi_dbg_print(int type, const char *func, const char *fmt, ...);
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void ubi_dbg_dump_ec_hdr(const struct ubi_ec_hdr *ec_hdr);
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void ubi_dbg_dump_vid_hdr(const struct ubi_vid_hdr *vid_hdr);
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void ubi_dbg_dump_vol_info(const struct ubi_volume *vol);
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void ubi_dbg_dump_vtbl_record(const struct ubi_vtbl_record *r, int idx);
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void ubi_dbg_dump_sv(const struct ubi_scan_volume *sv);
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void ubi_dbg_dump_seb(const struct ubi_scan_leb *seb, int type);
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void ubi_dbg_dump_mkvol_req(const struct ubi_mkvol_req *req);
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void ubi_dbg_hexdump(const void *buf, int size);
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#else
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#define dbg_msg(fmt, ...) ({})
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#define ubi_dbg_dump_stack() ({})
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#define ubi_dbg_print(func, fmt, ...) ({})
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#define ubi_dbg_dump_ec_hdr(ec_hdr) ({})
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#define ubi_dbg_dump_vid_hdr(vid_hdr) ({})
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#define ubi_dbg_dump_vol_info(vol) ({})
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#define ubi_dbg_dump_vtbl_record(r, idx) ({})
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#define ubi_dbg_dump_sv(sv) ({})
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#define ubi_dbg_dump_seb(seb, type) ({})
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#define ubi_dbg_dump_mkvol_req(req) ({})
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#define ubi_dbg_hexdump(buf, size) ({})
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#endif /* CONFIG_MTD_UBI_DEBUG_MSG */
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#ifdef CONFIG_MTD_UBI_DEBUG_MSG_EBA
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/* Messages from the eraseblock association unit */
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#define dbg_eba(fmt, ...) \
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printk(KERN_DEBUG "UBI DBG eba: %s: " fmt "\n", __FUNCTION__, \
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##__VA_ARGS__)
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#else
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#define dbg_eba(fmt, ...) ({})
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_MSG_WL
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/* Messages from the wear-leveling unit */
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#define dbg_wl(fmt, ...) \
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printk(KERN_DEBUG "UBI DBG wl: %s: " fmt "\n", __FUNCTION__, \
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##__VA_ARGS__)
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#else
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#define dbg_wl(fmt, ...) ({})
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_MSG_IO
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/* Messages from the input/output unit */
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#define dbg_io(fmt, ...) \
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printk(KERN_DEBUG "UBI DBG io: %s: " fmt "\n", __FUNCTION__, \
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##__VA_ARGS__)
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#else
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#define dbg_io(fmt, ...) ({})
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_MSG_BLD
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/* Initialization and build messages */
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#define dbg_bld(fmt, ...) \
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printk(KERN_DEBUG "UBI DBG bld: %s: " fmt "\n", __FUNCTION__, \
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##__VA_ARGS__)
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#else
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#define dbg_bld(fmt, ...) ({})
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_BITFLIPS
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/**
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* ubi_dbg_is_bitflip - if it is time to emulate a bit-flip.
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*
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* Returns non-zero if a bit-flip should be emulated, otherwise returns zero.
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*/
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static inline int ubi_dbg_is_bitflip(void)
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{
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return !(random32() % 200);
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}
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#else
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#define ubi_dbg_is_bitflip() 0
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_WRITE_FAILURES
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/**
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* ubi_dbg_is_write_failure - if it is time to emulate a write failure.
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*
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* Returns non-zero if a write failure should be emulated, otherwise returns
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* zero.
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*/
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static inline int ubi_dbg_is_write_failure(void)
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{
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return !(random32() % 500);
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}
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#else
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#define ubi_dbg_is_write_failure() 0
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#endif
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#ifdef CONFIG_MTD_UBI_DEBUG_EMULATE_ERASE_FAILURES
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/**
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* ubi_dbg_is_erase_failure - if its time to emulate an erase failure.
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*
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* Returns non-zero if an erase failure should be emulated, otherwise returns
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* zero.
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*/
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static inline int ubi_dbg_is_erase_failure(void)
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{
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return !(random32() % 400);
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}
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#else
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#define ubi_dbg_is_erase_failure() 0
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#endif
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#endif /* !__UBI_DEBUG_H__ */
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