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| -rw-r--r-- | Documentation/block/cmdline-partition.txt | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/block/cmdline-partition.txt b/Documentation/block/cmdline-partition.txt new file mode 100644 index 000000000..760a3f7c3 --- /dev/null +++ b/Documentation/block/cmdline-partition.txt @@ -0,0 +1,46 @@ +Embedded device command line partition parsing +===================================================================== + +The "blkdevparts" command line option adds support for reading the +block device partition table from the kernel command line. + +It is typically used for fixed block (eMMC) embedded devices. +It has no MBR, so saves storage space. Bootloader can be easily accessed +by absolute address of data on the block device. +Users can easily change the partition. + +The format for the command line is just like mtdparts: + +blkdevparts=<blkdev-def>[;<blkdev-def>] + <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>] + <partdef> := <size>[@<offset>](part-name) + +<blkdev-id> + block device disk name. Embedded device uses fixed block device. + Its disk name is also fixed, such as: mmcblk0, mmcblk1, mmcblk0boot0. + +<size> + partition size, in bytes, such as: 512, 1m, 1G. + size may contain an optional suffix of (upper or lower case): + K, M, G, T, P, E. + "-" is used to denote all remaining space. + +<offset> + partition start address, in bytes. + offset may contain an optional suffix of (upper or lower case): + K, M, G, T, P, E. + +(part-name) + partition name. Kernel sends uevent with "PARTNAME". Application can + create a link to block device partition with the name "PARTNAME". + User space application can access partition by partition name. + +Example: + eMMC disk names are "mmcblk0" and "mmcblk0boot0". + + bootargs: + 'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot),-(kernel)' + + dmesg: + mmcblk0: p1(data0) p2(data1) p3() + mmcblk0boot0: p1(boot) p2(kernel) |