Commit | Line | Data |
---|---|---|
898bd37a | 1 | ============================================== |
080506ad | 2 | Embedded device command line partition parsing |
898bd37a | 3 | ============================================== |
bab55417 | 4 | |
f6dbf65b RD |
5 | The "blkdevparts" command line option adds support for reading the |
6 | block device partition table from the kernel command line. | |
7 | ||
080506ad PG |
8 | It is typically used for fixed block (eMMC) embedded devices. |
9 | It has no MBR, so saves storage space. Bootloader can be easily accessed | |
bab55417 CZ |
10 | by absolute address of data on the block device. |
11 | Users can easily change the partition. | |
12 | ||
13 | The format for the command line is just like mtdparts: | |
14 | ||
15 | blkdevparts=<blkdev-def>[;<blkdev-def>] | |
16 | <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>] | |
17 | <partdef> := <size>[@<offset>](part-name) | |
18 | ||
19 | <blkdev-id> | |
f6dbf65b RD |
20 | block device disk name. Embedded device uses fixed block device. |
21 | Its disk name is also fixed, such as: mmcblk0, mmcblk1, mmcblk0boot0. | |
bab55417 CZ |
22 | |
23 | <size> | |
24 | partition size, in bytes, such as: 512, 1m, 1G. | |
f6dbf65b | 25 | size may contain an optional suffix of (upper or lower case): |
898bd37a | 26 | |
f6dbf65b | 27 | K, M, G, T, P, E. |
898bd37a | 28 | |
f6dbf65b | 29 | "-" is used to denote all remaining space. |
bab55417 CZ |
30 | |
31 | <offset> | |
32 | partition start address, in bytes. | |
f6dbf65b | 33 | offset may contain an optional suffix of (upper or lower case): |
898bd37a | 34 | |
f6dbf65b | 35 | K, M, G, T, P, E. |
bab55417 CZ |
36 | |
37 | (part-name) | |
f6dbf65b RD |
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. | |
bab55417 CZ |
41 | |
42 | Example: | |
898bd37a | 43 | |
f6dbf65b | 44 | eMMC disk names are "mmcblk0" and "mmcblk0boot0". |
bab55417 | 45 | |
898bd37a MCC |
46 | bootargs:: |
47 | ||
bab55417 CZ |
48 | 'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot),-(kernel)' |
49 | ||
898bd37a MCC |
50 | dmesg:: |
51 | ||
bab55417 CZ |
52 | mmcblk0: p1(data0) p2(data1) p3() |
53 | mmcblk0boot0: p1(boot) p2(kernel) |