Documentation/block/cmdline-partition.txt

   1 Embedded device command line partition parsing
   2 =====================================================================
   3
   4 Support for reading the block device partition table from the command line.
   5 It is typically used for fixed block (eMMC) embedded devices.
   6 It has no MBR, so saves storage space. Bootloader can be easily accessed
   7 by absolute address of data on the block device.
   8 Users can easily change the partition.
   9
  10 The format for the command line is just like mtdparts:
  11
  12 blkdevparts=<blkdev-def>[;<blkdev-def>]
  13   <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>]
  14     <partdef> := <size>[@<offset>](part-name)
  15
  16 <blkdev-id>
  17     block device disk name, embedded device used fixed block device,
  18     it's disk name also fixed. such as: mmcblk0, mmcblk1, mmcblk0boot0.
  19
  20 <size>
  21     partition size, in bytes, such as: 512, 1m, 1G.
  22
  23 <offset>
  24     partition start address, in bytes.
  25
  26 (part-name)
  27     partition name, kernel send uevent with "PARTNAME". application can create
  28     a link to block device partition with the name "PARTNAME".
  29     user space application can access partition by partition name.
  30
  31 Example:
  32     eMMC disk name is "mmcblk0" and "mmcblk0boot0"
  33
  34   bootargs:
  35     'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot),-(kernel)'
  36
  37   dmesg:
  38     mmcblk0: p1(data0) p2(data1) p3()
  39     mmcblk0boot0: p1(boot) p2(kernel)