Lenovo m720s combined audio jack not working (ALC233)

[Bastien Nocera]

On Tue, 2020-08-04 at 11:56 +0200, Bastien Nocera wrote:
> Hey,
> 
> The front audio jack on my newly purchased (but not new) Lenovo m720s
> doesn't make a microphone output appear in PulseAudio when a headset
> is
> plugged in. The headphone part works correctly though. The "sof-hda-
> dsp 
> Front Headphone" evdev device will switch the state of
> SW_HEADPHONE_INSERT as expected.
> 
> Does anyone know whether the headphones/headset switching is supposed
> to be automatic, or would that trigger a "what did you plug in"
> dialogue as on some Dell machines I've worked with?
> 
> I couldn't find any quirks in sound/pci/hda that would be directly
> related to this problem (eg. Lenovo, ALC233 and mic presence), so I'm
> a
> bit stumped.
> 
> I've attached the pinout information from alsa-info.

I should note that I'm using BIOS version M1UKT21A, and that the latest
is 25 releases newer, so that it's very possible that a newer BIOS
would fix this. I'll have to try that first.

Removed David from the CC:, as I don't have a current address for him.