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    mmc: add erase, secure erase, trim and secure trim operations · dfe86cba
    Adrian Hunter authored
    
    
    SD/MMC cards tend to support an erase operation.  In addition, eMMC v4.4
    cards can support secure erase, trim and secure trim operations that are
    all variants of the basic erase command.
    
    SD/MMC device attributes "erase_size" and "preferred_erase_size" have been
    added.
    
    "erase_size" is the minimum size, in bytes, of an erase operation.  For
    MMC, "erase_size" is the erase group size reported by the card.  Note that
    "erase_size" does not apply to trim or secure trim operations where the
    minimum size is always one 512 byte sector.  For SD, "erase_size" is 512
    if the card is block-addressed, 0 otherwise.
    
    SD/MMC cards can erase an arbitrarily large area up to and
    including the whole card.  When erasing a large area it may
    be desirable to do it in smaller chunks for three reasons:
    
        1. A single erase command will make all other I/O on the card
           wait.  This is not a problem if the whole card is being erased, but
           erasing one partition will make I/O for another partition on the
           same card wait for the duration of the erase - which could be a
           several minutes.
    
        2. To be able to inform the user of erase progress.
    
        3. The erase timeout becomes too large to be very useful.
           Because the erase timeout contains a margin which is multiplied by
           the size of the erase area, the value can end up being several
           minutes for large areas.
    
    "erase_size" is not the most efficient unit to erase (especially for SD
    where it is just one sector), hence "preferred_erase_size" provides a good
    chunk size for erasing large areas.
    
    For MMC, "preferred_erase_size" is the high-capacity erase size if a card
    specifies one, otherwise it is based on the capacity of the card.
    
    For SD, "preferred_erase_size" is the allocation unit size specified by
    the card.
    
    "preferred_erase_size" is in bytes.
    
    Signed-off-by: default avatarAdrian Hunter <adrian.hunter@nokia.com>
    Acked-by: default avatarJens Axboe <axboe@kernel.dk>
    Cc: Kyungmin Park <kmpark@infradead.org>
    Cc: Madhusudhan Chikkature <madhu.cr@ti.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Ben Gardiner <bengardiner@nanometrics.ca>
    Cc: <linux-mmc@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    dfe86cba