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Documentation / block / cmdline-partition.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:36 EST.

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)
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