[pulseaudio-discuss] [PATCH 4/4] alsa-mixer: Add "Headphone Mic" support for 3-pin ASUS netbooks

David Henningsson david.henningsson at canonical.com
Thu Jun 28 13:47:11 PDT 2012

On 06/28/2012 06:44 PM, Tanu Kaskinen wrote:
> On Thu, 2012-06-28 at 16:27 +0200, David Henningsson wrote:
>> Some ASUS netbooks, such as the 1015 CX, have only one 3.5 mm jack,
>> but it can be used either as a headphone or as a mic (but not both
>> simultaneously).
>> This patch adds support for the "Headphone Mic" path that is used
>> on these devices, so that we can use the jack as an external mic, and
>> doing so without muting the speaker.
>> BugLink: https://bugs.launchpad.net/bugs/1018262
>> Signed-off-by: David Henningsson <david.henningsson at canonical.com>
> The patch looks good to me, but I have a question: with this "Headphone
> Mic", will the associated input and output paths always have "unknown"
> as the availability state when there's something plugged in?

"Unknown" when it is plugged in, and "no" when it is unplugged. Maybe I 
should add the state.unplugged as well for clarity.

> Does alsa
> provide any means to figure out which one actually is being used, and if
> so, what are we missing in pulseaudio to make this work better?

There's no autodetection by the hardware of what has been plugged in.

The way it's implemented in ALSA is that there is a "Input Source" kctl, 
and if you set it to "Headphone Mic" the jack retasks as mic, and if you 
set it to "Internal Mic", the jack retasks as headphone.

In Windows 7, there is a popup when you plug in asking "Hey, what did 
you plug in?" and you select Headphone or Mic manually that way. I guess 
that would provide some extra level of elegance, but at least having a 
way of using the external mic would be good enough for me at this point.

David Henningsson, Canonical Ltd.

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