1============================================== 2Embedded device command line partition parsing 3============================================== 4 5The "blkdevparts" command line option adds support for reading the 6block device partition table from the kernel command line. 7 8It is typically used for fixed block (eMMC) embedded devices. 9It has no MBR, so saves storage space. Bootloader can be easily accessed 10by absolute address of data on the block device. 11Users can easily change the partition. 12 13The format for the command line is just like mtdparts: 14 15blkdevparts=<blkdev-def>[;<blkdev-def>] 16 <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>] 17 <partdef> := <size>[@<offset>](part-name) 18 19<blkdev-id> 20 block device disk name. Embedded device uses fixed block device. 21 Its disk name is also fixed, such as: mmcblk0, mmcblk1, mmcblk0boot0. 22 23<size> 24 partition size, in bytes, such as: 512, 1m, 1G. 25 size may contain an optional suffix of (upper or lower case): 26 27 K, M, G, T, P, E. 28 29 "-" is used to denote all remaining space. 30 31<offset> 32 partition start address, in bytes. 33 offset may contain an optional suffix of (upper or lower case): 34 35 K, M, G, T, P, E. 36 37(part-name) 38 partition name. Kernel sends uevent with "PARTNAME". Application can 39 create a link to block device partition with the name "PARTNAME". 40 User space application can access partition by partition name. 41 42ro 43 read-only. Flag the partition as read-only. 44 45Example: 46 47 eMMC disk names are "mmcblk0" and "mmcblk0boot0". 48 49 bootargs:: 50 51 'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot)ro,-(kernel)' 52 53 dmesg:: 54 55 mmcblk0: p1(data0) p2(data1) p3() 56 mmcblk0boot0: p1(boot) p2(kernel) 57