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371a689f64
Allows device MMC boot partitions to be accessed. MMC partitions are treated effectively as separate block devices on the same MMC card. Signed-off-by: Andrei Warkentin <andreiw@motorola.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Chris Ball <cjb@laptop.org>
28 lines
857 B
Plaintext
28 lines
857 B
Plaintext
SD and MMC Device Partitions
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============================
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Device partitions are additional logical block devices present on the
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SD/MMC device.
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As of this writing, MMC boot partitions as supported and exposed as
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/dev/mmcblkXboot0 and /dev/mmcblkXboot1, where X is the index of the
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parent /dev/mmcblkX.
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MMC Boot Partitions
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===================
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Read and write access is provided to the two MMC boot partitions. Due to
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the sensitive nature of the boot partition contents, which often store
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a bootloader or bootloader configuration tables crucial to booting the
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platform, write access is disabled by default to reduce the chance of
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accidental bricking.
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To enable write access to /dev/mmcblkXbootY, disable the forced read-only
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access with:
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echo 0 > /sys/block/mmcblkXbootY/force_ro
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To re-enable read-only access:
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echo 1 > /sys/block/mmcblkXbootY/force_ro
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