diff options
author | Linus Torvalds | 2019-07-16 21:21:41 +0200 |
---|---|---|
committer | Linus Torvalds | 2019-07-16 21:21:41 +0200 |
commit | c309b6f24222246c18a8b65d3950e6e755440865 (patch) | |
tree | 11893170f5c246bb0dee8066e85878af04162ab0 /Documentation/driver-api/mmc/mmc-dev-parts.rst | |
parent | Merge tag 'xtensa-20190715' of git://github.com/jcmvbkbc/linux-xtensa (diff) | |
parent | docs: kbuild: fix build with pdf and fix some minor issues (diff) | |
download | kernel-qcow2-linux-c309b6f24222246c18a8b65d3950e6e755440865.tar.gz kernel-qcow2-linux-c309b6f24222246c18a8b65d3950e6e755440865.tar.xz kernel-qcow2-linux-c309b6f24222246c18a8b65d3950e6e755440865.zip |
Merge tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull rst conversion of docs from Mauro Carvalho Chehab:
"As agreed with Jon, I'm sending this big series directly to you, c/c
him, as this series required a special care, in order to avoid
conflicts with other trees"
* tag 'docs/v5.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (77 commits)
docs: kbuild: fix build with pdf and fix some minor issues
docs: block: fix pdf output
docs: arm: fix a breakage with pdf output
docs: don't use nested tables
docs: gpio: add sysfs interface to the admin-guide
docs: locking: add it to the main index
docs: add some directories to the main documentation index
docs: add SPDX tags to new index files
docs: add a memory-devices subdir to driver-api
docs: phy: place documentation under driver-api
docs: serial: move it to the driver-api
docs: driver-api: add remaining converted dirs to it
docs: driver-api: add xilinx driver API documentation
docs: driver-api: add a series of orphaned documents
docs: admin-guide: add a series of orphaned documents
docs: cgroup-v1: add it to the admin-guide book
docs: aoe: add it to the driver-api book
docs: add some documentation dirs to the driver-api book
docs: driver-model: move it to the driver-api book
docs: lp855x-driver.rst: add it to the driver-api book
...
Diffstat (limited to 'Documentation/driver-api/mmc/mmc-dev-parts.rst')
-rw-r--r-- | Documentation/driver-api/mmc/mmc-dev-parts.rst | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/driver-api/mmc/mmc-dev-parts.rst b/Documentation/driver-api/mmc/mmc-dev-parts.rst new file mode 100644 index 000000000000..995922f1f744 --- /dev/null +++ b/Documentation/driver-api/mmc/mmc-dev-parts.rst @@ -0,0 +1,41 @@ +============================ +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 + +The boot partitions can also be locked read only until the next power on, +with:: + + echo 1 > /sys/block/mmcblkXbootY/ro_lock_until_next_power_on + +This is a feature of the card and not of the kernel. If the card does +not support boot partition locking, the file will not exist. If the +feature has been disabled on the card, the file will be read-only. + +The boot partitions can also be locked permanently, but this feature is +not accessible through sysfs in order to avoid accidental or malicious +bricking. |