SD and MMC Block Device Attributes

These attributes are defined for the block devices associated with the SD or MMC device.

The following attributes are read/write.


Enforce read-only access even if write protect switch is off.

SD and MMC Device Attributes

All attributes are read-only.


Card Identification Register


Card Specific Data Register


SD Card Configuration Register (SD only)


Manufacturing Date (from CID Register)


Firmware/Product Revision (from CID Register) (SD and MMCv1 only)


Hardware/Product Revision (from CID Register) (SD and MMCv1 only)


Manufacturer ID (from CID Register)


Product Name (from CID Register)


OEM/Application ID (from CID Register)


Product Revision (from CID Register) (SD and MMCv4 only)


Product Serial Number (from CID Register)


Erase group size


Preferred erase size


RPMB partition size


Reliable write sector count


Operation Conditions Register


Driver Stage Register


Command Queue enabled:

1 => enabled, 0 => not enabled

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.

Note on raw_rpmb_size_mult:

"raw_rpmb_size_mult" is a multiple of 128kB block.

RPMB size in byte is calculated by using the following equation:

RPMB partition size = 128kB x raw_rpmb_size_mult