Unverified Commit d86300cc authored Jun 12, 2020 by Usama Arif

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

parent c3f17840

init/devices.cpp

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;