Comment 22 for bug 284319
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| Dana Goyette (danagoyette) wrote Re: mute, brightness buttons on new HP 6930p laptop | #22 |
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0e1f616
(Get the code!)
Now I've figured out a bit more about the GPIO usage:
GPIO 0 (input) acts as headphone detection -- 0 if present, 1 if absent.
GPIO 1 (output) controls muting and LED -- active high ('1' mutes).
GPIO 2 (input) returns LED status (pressing hardware button toggles it) -- active high.
It seems ALSA needs to watch GPIO 2, and when it detects a change, it must update the software mixer status, update GPIO 1 value, and send a "display the volume without changing it" event of some sort (as is done with the Thinkpad hardware volume control).