[alsa-devel] CX20724 headset button detect

[David Woodhouse]

I have an HP EliteBook 850 G3 with CX20724:

 hdaudioC0D0: CX20724: BIOS auto-probing.
 hdaudioC0D0: action: 0 gpio_led: 0
 hdaudioC0D0: autoconfig for CX20724: line_outs=1 (0x16/0x0/0x0/0x0/0x0) type:line
 hdaudioC0D0:    speaker_outs=1 (0x17/0x0/0x0/0x0/0x0)
 hdaudioC0D0:    hp_outs=1 (0x1d/0x0/0x0/0x0/0x0)
 hdaudioC0D0:    mono: mono_out=0x0
 hdaudioC0D0:    inputs:
 hdaudioC0D0:      Mic=0x19
 hdaudioC0D0:      Internal Mic=0x1a
 hdaudioC0D0:      Line=0x18
 hdaudioC0D0: Enable sync_write for stable communication
 hdaudioC0D0: action: 1 gpio_led: 0
 hdaudioC0D0: action: 2 gpio_led: 0
 ...
 input: HDA Intel PCH Mic as /devices/pci0000:00/0000:00:1f.3/sound/card0/input21

The CX20724 datasheet¹ suggests that it supports headset button events
— at least 'Function A' when the mic pin is shorted to ground, if not
the other functions.

But it isn't working. Only the jack insertion is reported through the
corresponding input device, not the button press. I added a printk into
snd_hda_jack_unsol_event(), and it isn't even being invoked at all for
the button presses; only insertion/removal.

How do we make this work?


¹ https://www.tonymacx86.com/attachments/datasheet_cx20724-pdf.203615/
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