54 lines
1.6 KiB
ReStructuredText
54 lines
1.6 KiB
ReStructuredText
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==============================================
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Embedded device command line partition parsing
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==============================================
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The "blkdevparts" command line option adds support for reading the
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block device partition table from the kernel command line.
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It is typically used for fixed block (eMMC) embedded devices.
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It has no MBR, so saves storage space. Bootloader can be easily accessed
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by absolute address of data on the block device.
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Users can easily change the partition.
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The format for the command line is just like mtdparts:
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blkdevparts=<blkdev-def>[;<blkdev-def>]
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<blkdev-def> := <blkdev-id>:<partdef>[,<partdef>]
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<partdef> := <size>[@<offset>](part-name)
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<blkdev-id>
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block device disk name. Embedded device uses fixed block device.
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Its disk name is also fixed, such as: mmcblk0, mmcblk1, mmcblk0boot0.
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<size>
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partition size, in bytes, such as: 512, 1m, 1G.
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size may contain an optional suffix of (upper or lower case):
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K, M, G, T, P, E.
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"-" is used to denote all remaining space.
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<offset>
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partition start address, in bytes.
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offset may contain an optional suffix of (upper or lower case):
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K, M, G, T, P, E.
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(part-name)
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partition name. Kernel sends uevent with "PARTNAME". Application can
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create a link to block device partition with the name "PARTNAME".
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User space application can access partition by partition name.
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Example:
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eMMC disk names are "mmcblk0" and "mmcblk0boot0".
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bootargs::
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'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot),-(kernel)'
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dmesg::
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mmcblk0: p1(data0) p2(data1) p3()
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mmcblk0boot0: p1(boot) p2(kernel)
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