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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>
152 lines
4.3 KiB
C
152 lines
4.3 KiB
C
/*
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* $Id: mtd-abi.h,v 1.13 2005/11/07 11:14:56 gleixner Exp $
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*
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* Portions of MTD ABI definition which are shared by kernel and user space
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*/
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#ifndef __MTD_ABI_H__
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#define __MTD_ABI_H__
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struct erase_info_user {
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uint32_t start;
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uint32_t length;
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};
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struct mtd_oob_buf {
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uint32_t start;
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uint32_t length;
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unsigned char __user *ptr;
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};
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#define MTD_ABSENT 0
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#define MTD_RAM 1
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#define MTD_ROM 2
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#define MTD_NORFLASH 3
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#define MTD_NANDFLASH 4
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#define MTD_DATAFLASH 6
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#define MTD_UBIVOLUME 7
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#define MTD_WRITEABLE 0x400 /* Device is writeable */
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#define MTD_BIT_WRITEABLE 0x800 /* Single bits can be flipped */
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#define MTD_NO_ERASE 0x1000 /* No erase necessary */
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#define MTD_STUPID_LOCK 0x2000 /* Always locked after reset */
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// Some common devices / combinations of capabilities
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#define MTD_CAP_ROM 0
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#define MTD_CAP_RAM (MTD_WRITEABLE | MTD_BIT_WRITEABLE | MTD_NO_ERASE)
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#define MTD_CAP_NORFLASH (MTD_WRITEABLE | MTD_BIT_WRITEABLE)
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#define MTD_CAP_NANDFLASH (MTD_WRITEABLE)
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/* ECC byte placement */
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#define MTD_NANDECC_OFF 0 // Switch off ECC (Not recommended)
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#define MTD_NANDECC_PLACE 1 // Use the given placement in the structure (YAFFS1 legacy mode)
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#define MTD_NANDECC_AUTOPLACE 2 // Use the default placement scheme
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#define MTD_NANDECC_PLACEONLY 3 // Use the given placement in the structure (Do not store ecc result on read)
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#define MTD_NANDECC_AUTOPL_USR 4 // Use the given autoplacement scheme rather than using the default
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/* OTP mode selection */
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#define MTD_OTP_OFF 0
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#define MTD_OTP_FACTORY 1
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#define MTD_OTP_USER 2
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struct mtd_info_user {
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uint8_t type;
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uint32_t flags;
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uint32_t size; // Total size of the MTD
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uint32_t erasesize;
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uint32_t writesize;
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uint32_t oobsize; // Amount of OOB data per block (e.g. 16)
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/* The below two fields are obsolete and broken, do not use them
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* (TODO: remove at some point) */
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uint32_t ecctype;
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uint32_t eccsize;
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};
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struct region_info_user {
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uint32_t offset; /* At which this region starts,
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* from the beginning of the MTD */
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uint32_t erasesize; /* For this region */
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uint32_t numblocks; /* Number of blocks in this region */
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uint32_t regionindex;
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};
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struct otp_info {
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uint32_t start;
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uint32_t length;
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uint32_t locked;
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};
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#define MEMGETINFO _IOR('M', 1, struct mtd_info_user)
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#define MEMERASE _IOW('M', 2, struct erase_info_user)
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#define MEMWRITEOOB _IOWR('M', 3, struct mtd_oob_buf)
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#define MEMREADOOB _IOWR('M', 4, struct mtd_oob_buf)
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#define MEMLOCK _IOW('M', 5, struct erase_info_user)
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#define MEMUNLOCK _IOW('M', 6, struct erase_info_user)
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#define MEMGETREGIONCOUNT _IOR('M', 7, int)
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#define MEMGETREGIONINFO _IOWR('M', 8, struct region_info_user)
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#define MEMSETOOBSEL _IOW('M', 9, struct nand_oobinfo)
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#define MEMGETOOBSEL _IOR('M', 10, struct nand_oobinfo)
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#define MEMGETBADBLOCK _IOW('M', 11, loff_t)
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#define MEMSETBADBLOCK _IOW('M', 12, loff_t)
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#define OTPSELECT _IOR('M', 13, int)
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#define OTPGETREGIONCOUNT _IOW('M', 14, int)
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#define OTPGETREGIONINFO _IOW('M', 15, struct otp_info)
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#define OTPLOCK _IOR('M', 16, struct otp_info)
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#define ECCGETLAYOUT _IOR('M', 17, struct nand_ecclayout)
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#define ECCGETSTATS _IOR('M', 18, struct mtd_ecc_stats)
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#define MTDFILEMODE _IO('M', 19)
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/*
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* Obsolete legacy interface. Keep it in order not to break userspace
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* interfaces
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*/
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struct nand_oobinfo {
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uint32_t useecc;
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uint32_t eccbytes;
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uint32_t oobfree[8][2];
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uint32_t eccpos[32];
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};
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struct nand_oobfree {
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uint32_t offset;
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uint32_t length;
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};
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#define MTD_MAX_OOBFREE_ENTRIES 8
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/*
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* ECC layout control structure. Exported to userspace for
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* diagnosis and to allow creation of raw images
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*/
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struct nand_ecclayout {
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uint32_t eccbytes;
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uint32_t eccpos[64];
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uint32_t oobavail;
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struct nand_oobfree oobfree[MTD_MAX_OOBFREE_ENTRIES];
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};
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/**
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* struct mtd_ecc_stats - error correction stats
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*
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* @corrected: number of corrected bits
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* @failed: number of uncorrectable errors
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* @badblocks: number of bad blocks in this partition
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* @bbtblocks: number of blocks reserved for bad block tables
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*/
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struct mtd_ecc_stats {
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uint32_t corrected;
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uint32_t failed;
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uint32_t badblocks;
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uint32_t bbtblocks;
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};
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/*
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* Read/write file modes for access to MTD
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*/
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enum mtd_file_modes {
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MTD_MODE_NORMAL = MTD_OTP_OFF,
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MTD_MODE_OTP_FACTORY = MTD_OTP_FACTORY,
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MTD_MODE_OTP_USER = MTD_OTP_USER,
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MTD_MODE_RAW,
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};
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#endif /* __MTD_ABI_H__ */
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