Kernel-2.6.32-573.12.1.el6_mmc-dev-attrs

SD and MMC Device Attributes

All attributes are read-only.

cid            Card Identifaction Register
csd            Card Specific Data Register
scr            SD Card Configuration Register (SD only)
date            Manufacturing Date (from CID Register)
fwrev            Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
hwrev            Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
manfid            Manufacturer ID (from CID Register)
name            Product Name (from CID Register)
oemid            OEM/Application ID (from CID Register)
serial            Product Serial Number (from CID Register)
erase_size        Erase group size
preferred_erase_size    Preferred erase size

Note on Erase Size and Preferred Erase Size:

"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.