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Add AMBA bus support to platform devices 

AMBA specification from Arm is a freely available open
standard for the connection and management of functional
blocks in a system-on-chip.
AMBA devices create a device kernel object in /sys/devices/platform
and a kernel object of the bus for the respective device in
/sys/bus/amba. For e.g. for pl180 mmc:
device: /sys/devices/platform/1c050000.mmci
bus: /sys/bus/amba/devices/1c050000.mmci

In first stage init, android creates a symlink from /sys/devices/platform/...
to /dev/block/platform/... for all partitions and then to
/dev/block/by-name for the boot_device used. However this is only done
for devices that "attach" to bus/platform. This patch adds support for
platform devices that attach to bus/amba.

Signed-off-by: Usama Arif <usama.arif@arm.com>
Change-Id: I9da7456407c4f62335c959502d8b2d16026fddfc
This commit is contained in:
Usama Arif 2020-06-12 13:45:11 +01:00
parent c3f17840ae
commit d86300cc7e
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1 changed files with 2 additions and 1 deletions
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3
init/devices.cpp
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@ -193,7 +193,8 @@ bool DeviceHandler::FindPlatformDevice(std::string path, std::string* platform_d
while (directory != "/" && directory != ".") {
std::string subsystem_link_path;
if (Realpath(directory + "/subsystem", &subsystem_link_path) &&
subsystem_link_path == sysfs_mount_point_ + "/bus/platform") {
(subsystem_link_path == sysfs_mount_point_ + "/bus/platform" ||
subsystem_link_path == sysfs_mount_point_ + "/bus/amba")) {
// We need to remove the mount point that we added above before returning.
directory.erase(0, sysfs_mount_point_.size());
*platform_device_path = directory;