[alsa-devel] Regression for Lenovo X240 sound in 3.18

[Raymond Yau]

> >
> >If Combo audio connector does not support conventional microphone, this
mean
> >the driver should not create mic jack control for node 0x1a
> >
> >http://support.lenovo.com/us/en/documents/pd029567
> >
> >Connect headphones or a headset that has a 3.5-mm (0.14-inch), 4-pole
plug
> >to the combo audio connector to listen to the sound from the computer.
>
> I do not have any 4-pole (3-rings) equipment to test.
> A conventional 3-pole (2-ring) microphone certainly does not do its job.
>
> Then again, I ditched unpowered microphones (most external ones are).
> The internal mic next to the internal webcam is powered and provides
> better gain.
>
> The Mic control in alsamixer should stay.

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/pci/hda?id=73bdd597823e2231dc882577dbbaf8df92fe1775

The debug version of driver  message indicate whether the codec can
differentiate headphone , headset (ctia or omtp) or not

http://voices.canonical.com/david.henningsson/2014/03/07/headset-jacks-on-newer-laptops/

http://bazaar.launchpad.net/~unity-settings-daemon-team/unity-settings-daemon/trunk/view/head:/plugins/media-keys/what-did-you-plug-in/pa-backend.c

Headphone Mic Jack - indicates headphone and mic-in mode share the same
jack,  i e, not two separate jacks. Hardware cannot distinguish between a
headphone and a mic.
   Headset Mic Phantom Jack - indicates headset jack where hardware can not
distinguish between headphones and headsets
   Headset Mic Jack - indicates headset jack where hardware can distinguish
between headphones and headsets. There is no use popping up a dialog in
this case, unless we already need to do this for the mic-in mode.

control.14 {
iface CARD
name 'Mic Jack'
value false
comment { access read type BOOLEAN count 1 } }

What is the usage of this jack detect control if conventional mic is not
supported ?