linux/drivers/mtd/ubi/gluebi.c

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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>
2006-06-27 08:22:22 +00:00
/*
* Copyright (c) International Business Machines Corp., 2006
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
* the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author: Artem Bityutskiy (Битюцкий Артём), Joern Engel
*/
/*
* This file includes implementation of fake MTD devices for each UBI volume.
* This sounds strange, but it is in fact quite useful to make MTD-oriented
* software (including all the legacy software) to work on top of UBI.
*
* Gluebi emulates MTD devices of "MTD_UBIVOLUME" type. Their minimal I/O unit
* size (mtd->writesize) is equivalent to the UBI minimal I/O unit. The
* eraseblock size is equivalent to the logical eraseblock size of the volume.
*/
#include <asm/div64.h>
#include "ubi.h"
/**
* gluebi_get_device - get MTD device reference.
* @mtd: the MTD device description object
*
* This function is called every time the MTD device is being opened and
* implements the MTD get_device() operation. Returns zero in case of success
* and a negative error code in case of failure.
*/
static int gluebi_get_device(struct mtd_info *mtd)
{
struct ubi_volume *vol;
vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
/*
* We do not introduce locks for gluebi reference count because the
* get_device()/put_device() calls are already serialized at MTD.
*/
if (vol->gluebi_refcount > 0) {
/*
* The MTD device is already referenced and this is just one
* more reference. MTD allows many users to open the same
* volume simultaneously and do not distinguish between
* readers/writers/exclusive openers as UBI does. So we do not
* open the UBI volume again - just increase the reference
* counter and return.
*/
vol->gluebi_refcount += 1;
return 0;
}
/*
* This is the first reference to this UBI volume via the MTD device
* interface. Open the corresponding volume in read-write mode.
*/
vol->gluebi_desc = ubi_open_volume(vol->ubi->ubi_num, vol->vol_id,
UBI_READWRITE);
if (IS_ERR(vol->gluebi_desc))
return PTR_ERR(vol->gluebi_desc);
vol->gluebi_refcount += 1;
return 0;
}
/**
* gluebi_put_device - put MTD device reference.
* @mtd: the MTD device description object
*
* This function is called every time the MTD device is being put. Returns
* zero in case of success and a negative error code in case of failure.
*/
static void gluebi_put_device(struct mtd_info *mtd)
{
struct ubi_volume *vol;
vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
vol->gluebi_refcount -= 1;
ubi_assert(vol->gluebi_refcount >= 0);
if (vol->gluebi_refcount == 0)
ubi_close_volume(vol->gluebi_desc);
}
/**
* gluebi_read - read operation of emulated MTD devices.
* @mtd: MTD device description object
* @from: absolute offset from where to read
* @len: how many bytes to read
* @retlen: count of read bytes is returned here
* @buf: buffer to store the read data
*
* This function returns zero in case of success and a negative error code in
* case of failure.
*/
static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
size_t *retlen, unsigned char *buf)
{
int err = 0, lnum, offs, total_read;
struct ubi_volume *vol;
struct ubi_device *ubi;
uint64_t tmp = from;
dbg_msg("read %zd bytes from offset %lld", len, from);
if (len < 0 || from < 0 || from + len > mtd->size)
return -EINVAL;
vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
ubi = vol->ubi;
offs = do_div(tmp, mtd->erasesize);
lnum = tmp;
total_read = len;
while (total_read) {
size_t to_read = mtd->erasesize - offs;
if (to_read > total_read)
to_read = total_read;
err = ubi_eba_read_leb(ubi, vol, lnum, buf, offs, to_read, 0);
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>
2006-06-27 08:22:22 +00:00
if (err)
break;
lnum += 1;
offs = 0;
total_read -= to_read;
buf += to_read;
}
*retlen = len - total_read;
return err;
}
/**
* gluebi_write - write operation of emulated MTD devices.
* @mtd: MTD device description object
* @to: absolute offset where to write
* @len: how many bytes to write
* @retlen: count of written bytes is returned here
* @buf: buffer with data to write
*
* This function returns zero in case of success and a negative error code in
* case of failure.
*/
static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
size_t *retlen, const u_char *buf)
{
int err = 0, lnum, offs, total_written;
struct ubi_volume *vol;
struct ubi_device *ubi;
uint64_t tmp = to;
dbg_msg("write %zd bytes to offset %lld", len, to);
if (len < 0 || to < 0 || len + to > mtd->size)
return -EINVAL;
vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
ubi = vol->ubi;
if (ubi->ro_mode)
return -EROFS;
offs = do_div(tmp, mtd->erasesize);
lnum = tmp;
if (len % mtd->writesize || offs % mtd->writesize)
return -EINVAL;
total_written = len;
while (total_written) {
size_t to_write = mtd->erasesize - offs;
if (to_write > total_written)
to_write = total_written;
err = ubi_eba_write_leb(ubi, vol, lnum, buf, offs, to_write,
UBI_UNKNOWN);
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>
2006-06-27 08:22:22 +00:00
if (err)
break;
lnum += 1;
offs = 0;
total_written -= to_write;
buf += to_write;
}
*retlen = len - total_written;
return err;
}
/**
* gluebi_erase - erase operation of emulated MTD devices.
* @mtd: the MTD device description object
* @instr: the erase operation description
*
* This function calls the erase callback when finishes. Returns zero in case
* of success and a negative error code in case of failure.
*/
static int gluebi_erase(struct mtd_info *mtd, struct erase_info *instr)
{
int err, i, lnum, count;
struct ubi_volume *vol;
struct ubi_device *ubi;
dbg_msg("erase %u bytes at offset %u", instr->len, instr->addr);
if (instr->addr < 0 || instr->addr > mtd->size - mtd->erasesize)
return -EINVAL;
if (instr->len < 0 || instr->addr + instr->len > mtd->size)
return -EINVAL;
if (instr->addr % mtd->writesize || instr->len % mtd->writesize)
return -EINVAL;
lnum = instr->addr / mtd->erasesize;
count = instr->len / mtd->erasesize;
vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
ubi = vol->ubi;
if (ubi->ro_mode)
return -EROFS;
for (i = 0; i < count; i++) {
err = ubi_eba_unmap_leb(ubi, vol, lnum + i);
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>
2006-06-27 08:22:22 +00:00
if (err)
goto out_err;
}
/*
* MTD erase operations are synchronous, so we have to make sure the
* physical eraseblock is wiped out.
*/
err = ubi_wl_flush(ubi);
if (err)
goto out_err;
instr->state = MTD_ERASE_DONE;
mtd_erase_callback(instr);
return 0;
out_err:
instr->state = MTD_ERASE_FAILED;
instr->fail_addr = lnum * mtd->erasesize;
return err;
}
/**
* ubi_create_gluebi - initialize gluebi for an UBI volume.
* @ubi: UBI device description object
* @vol: volume description object
*
* This function is called when an UBI volume is created in order to create
* corresponding fake MTD device. Returns zero in case of success and a
* negative error code in case of failure.
*/
int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol)
{
struct mtd_info *mtd = &vol->gluebi_mtd;
mtd->name = kmemdup(vol->name, vol->name_len + 1, GFP_KERNEL);
if (!mtd->name)
return -ENOMEM;
mtd->type = MTD_UBIVOLUME;
if (!ubi->ro_mode)
mtd->flags = MTD_WRITEABLE;
mtd->writesize = ubi->min_io_size;
mtd->owner = THIS_MODULE;
mtd->erasesize = vol->usable_leb_size;
mtd->read = gluebi_read;
mtd->write = gluebi_write;
mtd->erase = gluebi_erase;
mtd->get_device = gluebi_get_device;
mtd->put_device = gluebi_put_device;
/*
* In case of dynamic volume, MTD device size is just volume size. In
* case of a static volume the size is equivalent to the amount of data
* bytes.
*/
if (vol->vol_type == UBI_DYNAMIC_VOLUME)
mtd->size = vol->usable_leb_size * vol->reserved_pebs;
else
mtd->size = vol->used_bytes;
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>
2006-06-27 08:22:22 +00:00
if (add_mtd_device(mtd)) {
ubi_err("cannot not add MTD device\n");
kfree(mtd->name);
return -ENFILE;
}
dbg_msg("added mtd%d (\"%s\"), size %u, EB size %u",
mtd->index, mtd->name, mtd->size, mtd->erasesize);
return 0;
}
/**
* ubi_destroy_gluebi - close gluebi for an UBI volume.
* @vol: volume description object
*
* This function is called when an UBI volume is removed in order to remove
* corresponding fake MTD device. Returns zero in case of success and a
* negative error code in case of failure.
*/
int ubi_destroy_gluebi(struct ubi_volume *vol)
{
int err;
struct mtd_info *mtd = &vol->gluebi_mtd;
dbg_msg("remove mtd%d", mtd->index);
err = del_mtd_device(mtd);
if (err)
return err;
kfree(mtd->name);
return 0;
}
/**
* ubi_gluebi_updated - UBI volume was updated notifier.
* @vol: volume description object
*
* This function is called every time an UBI volume is updated. This function
* does nothing if volume @vol is dynamic, and changes MTD device size if the
* volume is static. This is needed because static volumes cannot be read past
* data they contain.
*/
void ubi_gluebi_updated(struct ubi_volume *vol)
{
struct mtd_info *mtd = &vol->gluebi_mtd;
if (vol->vol_type == UBI_STATIC_VOLUME)
mtd->size = vol->used_bytes;
}