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