init: create symlinks to block device nodes
eMMC block device names may change based on the detection order of
the eMMC device and any other SD bus devices, such as a removable SD
card.
This patch adds support to init for:
* Symlinks to block devices. When a block device uevent is
processed, if it starts with "/devices/platform", the platform
driver name is parsed out, and symlinks to the block device are
created in /dev/block/platform/<platform driver>/
* Symlinks based on partition name and number. If the uevent for
a block device contains information on the partition name or
number, symlinks are created under
/dev/block/platform/<platform driver>/by-num/p<partition>
and
/dev/block/platform/<platform driver>/by-name/<partition name>
init.rc can then use a device path like the following to mount an
eMMC device:
/dev/block/platform/<platform>/by-name/system /system ro
Change-Id:
Id11bb7cdf1e2ada7752a5bd671cbf87237b34ae2
详细的patch文件请见：
因为uevent文件是init的一个符号链接，主要原理就是uevent事件来了之后进行判断，是否是
/devices/platform，是的话则分析创建符号链接
+ if (!strncmp(uevent->path, "/devices/platform/", 18))
+ links = parse_platform_block_device(uevent);