| SD and MMC Device Partitions |
| ============================ |
| |
| Device partitions are additional logical block devices present on the |
| SD/MMC device. |
| |
| As of this writing, MMC boot partitions as supported and exposed as |
| /dev/mmcblkXboot0 and /dev/mmcblkXboot1, where X is the index of the |
| parent /dev/mmcblkX. |
| |
| MMC Boot Partitions |
| =================== |
| |
| Read and write access is provided to the two MMC boot partitions. Due to |
| the sensitive nature of the boot partition contents, which often store |
| a bootloader or bootloader configuration tables crucial to booting the |
| platform, write access is disabled by default to reduce the chance of |
| accidental bricking. |
| |
| To enable write access to /dev/mmcblkXbootY, disable the forced read-only |
| access with: |
| |
| echo 0 > /sys/block/mmcblkXbootY/force_ro |
| |
| To re-enable read-only access: |
| |
| echo 1 > /sys/block/mmcblkXbootY/force_ro |
