Eric Lee / smarc-fsl-linux-kernel

06 Jun, 2009

1 commit

  • 24430abc8   Kill jffs2-user.h ... Browse Code »

    This file does not define any kernel-userspace API, all
    it does it defines few helpers for userspace. Instead,
    userspace should have a private copy of this file.

    The main (if not the only) user is the mtd-utils package, but
    it already has a private copy of this file.

    This patch also removes references to 'jffs2-user.h' from
    'Kbuild' and MAINTAINERS' files.

    Signed-off-by: Artem Bityutskiy
    Signed-off-by: David Woodhouse

    Artem Bityutskiy
     

17 Apr, 2008

1 commit

  • 92a74f1c1   UBI: make ubi-header.h local ... Browse Code »

    The new trend in linux is not to store headers which define
    on-media format in the include/ directory, but instead, store
    them locally. This is because these headers "do not define any
    kerneluserspace interface".

    Do so for UBI as well.

    Signed-off-by: Artem Bityutskiy

    Artem Bityutskiy
     

27 Apr, 2007

1 commit

  • 801c135ce   UBI: Unsorted Block Images ... Browse Code »

    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
    Signed-off-by: Frank Haverkamp

    Artem B. Bityutskiy
     

02 Oct, 2006

1 commit

26 Sep, 2006

1 commit

19 Sep, 2006

1 commit

18 Jun, 2006

1 commit