Load soc_button_array module on Surface

[FloofyPeachy]

On Microsoft Surface devices, the power and volume buttons are handled by soc_button_array. The commit enables this functionality in Android by loading the soc_button_array kernel module on startup.

(This is my first commit to Bliss btw, lmk if there's a different place I should push this)

[hmtheboy154]

oh so it didn't load automatically huh

[hmtheboy154]

Do you want we instead put CONFIG_INPUT_SOC_BUTTON_ARRAY into the kernel so you don't have to load ?

[FloofyPeachy]

Sure, that will work!!

[jwrdegoede]

On standard Linux distributions (still learning how Android does things) soc_button_array indeed should autoload if build as a module. It binds to the platform_device the ACPI subsystem creates for it based on the following acpi_device_id-s: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/misc/soc_button_array.c#n598

And there is a MODULE_DEVICE_TABLE(acpi, soc_button_acpi_match); line there which causes modalias to be created for all those matches. So on standard Linux udev will call modprobe for the modalias of the platform_device.

So e.g. doing a cat on a modalias file for an involved platform_device will show:

# cat /sys/bus/platform/devices/INT33D3\:00/modalias
acpi:INT33D3:PNP0C60:

and then udev will run modprobe acpi:INT33D3:PNP0C60: which matches one of the modaliases for the module:

# modinfo soc_button_array | grep INT33D3
alias:          acpi*:INT33D3:*

So modprobe will then load soc_button_array. I have no idea if Android even has modprobe, I think it typically has init scripts which hardcode a bunch of insmod commands instead? And if Android does have modprobe I don't know if something is running "modprobe " for all devices with a uevent sysfs attribute like udev does (I believe that Android has its own udev equivalent, right?) .

[jwrdegoede]

Note if you want to give the above comments a try on Surface devices the soc_button_array driver uses MSHW0028 or MSHW0040 as ACPI Hardware ID (aka HID).

[hmtheboy154]

So modprobe will then load soc_button_array. I have no idea if Android even has modprobe, I think it typically has init scripts which hardcode a bunch of insmod commands instead? And if Android does have modprobe I don't know if something is running "modprobe " for all devices with a uevent sysfs attribute like udev does (I believe that Android has its own udev equivalent, right?) .

We do have modprobe
https://github.com/BlissOS/platform_system_core/blob/typhoon-x86/toolbox/modprobe.cpp

And we use modalias_handling on ueventd to let it automatically load modules
BlissOS/platform_system_core@db19de3#diff-17392ed5df252d7e6293da185ba9563b642aabb17017cbded41ac62638ee3df3