• Ezequiel Garcia's avatar
    UBI: R/O block driver on top of UBI volumes · 9d54c8a3
    Ezequiel Garcia authored
    This commit introduces read-only block device emulation on top of UBI volumes.
    
    Given UBI takes care of wear leveling and bad block management it's possible
    to add a thin layer to enable block device access to UBI volumes.
    This allows to use a block-oriented filesystem on a flash device.
    
    The UBI block devices are meant to be used in conjunction with any
    regular, block-oriented file system (e.g. ext4), although it's primarily
    targeted at read-only file systems, such as squashfs.
    
    Block devices are created upon user request through new ioctls:
    UBI_IOCVOLATTBLK to attach and UBI_IOCVOLDETBLK to detach.
    Also, a new UBI module parameter is added 'ubi.block'. This parameter is
    needed in order to attach a block device on boot-up time, allowing to
    mount the rootfs on a ubiblock device.
    For instance, you could have these kernel parameters:
    
      ubi.mtd=5 ubi.block=0,0 root=/dev/ubiblock0_0
    
    Or, if you compile ubi as a module:
    
      $ modprobe ubi mtd=/dev/mtd5 block=/dev/ubi0_0
    
    Artem: amend commentaries and massage the patch a little bit.
    Signed-off-by: default avatarEzequiel Garcia <ezequiel.garcia@free-electrons.com>
    Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
    9d54c8a3
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