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authorAndrei Warkentin <andreiw@motorola.com>2011-04-11 18:10:25 -0500
committerChris Ball <cjb@laptop.org>2011-05-24 21:01:21 -0400
commit371a689f64b0da140c3bcd3f55305ffa1c3a58ef (patch)
treec0dff82d668378d395cb22ce33cd93e6dafef9eb /Documentation/mmc/mmc-dev-parts.txt
parent1a258db6f396e26c2c00b19c0107a891895d4584 (diff)
mmc: MMC boot partitions support.
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>
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+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