From 371a689f64b0da140c3bcd3f55305ffa1c3a58ef Mon Sep 17 00:00:00 2001 From: Andrei Warkentin Date: Mon, 11 Apr 2011 18:10:25 -0500 Subject: 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 Acked-by: Arnd Bergmann Signed-off-by: Chris Ball --- Documentation/mmc/00-INDEX | 2 ++ Documentation/mmc/mmc-dev-attrs.txt | 10 ++++++++++ Documentation/mmc/mmc-dev-parts.txt | 27 +++++++++++++++++++++++++++ 3 files changed, 39 insertions(+) create mode 100644 Documentation/mmc/mmc-dev-parts.txt (limited to 'Documentation/mmc') diff --git a/Documentation/mmc/00-INDEX b/Documentation/mmc/00-INDEX index fca586f5b853..93dd7a714075 100644 --- a/Documentation/mmc/00-INDEX +++ b/Documentation/mmc/00-INDEX @@ -2,3 +2,5 @@ - this file mmc-dev-attrs.txt - info on SD and MMC device attributes +mmc-dev-parts.txt + - info on SD and MMC device partitions diff --git a/Documentation/mmc/mmc-dev-attrs.txt b/Documentation/mmc/mmc-dev-attrs.txt index ff2bd685bced..8898a95b41e5 100644 --- a/Documentation/mmc/mmc-dev-attrs.txt +++ b/Documentation/mmc/mmc-dev-attrs.txt @@ -1,3 +1,13 @@ +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. + + force_ro Enforce read-only access even if write protect switch is off. + SD and MMC Device Attributes ============================ diff --git a/Documentation/mmc/mmc-dev-parts.txt b/Documentation/mmc/mmc-dev-parts.txt new file mode 100644 index 000000000000..2db28b8e662f --- /dev/null +++ b/Documentation/mmc/mmc-dev-parts.txt @@ -0,0 +1,27 @@ +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 -- cgit v1.2.3-59-g8ed1b