[pulseaudio-discuss] Alsa with UCM, input device-based jack detection

Tanu Kaskinen tanuk at iki.fi
Fri Sep 30 09:46:52 UTC 2016

On Thu, 2016-09-22 at 18:15 +0200, Paul Kocialkowski wrote:
> Hi,
> I'm trying to get Jack detection with ALSA UCM working nicely on an ARM platform
> but I am currently hitting a few issues. In the kernel, soc-jack (used on e.g.
> ARM SoCs) will not create a kcontrol so the JackControl property can't be used
> directly (as far as I have understood). Some UCM files provide "JackName" to
> specify the input device name to use, which is provided in the ASoC case.

My impression is that nowadays the kernel automatically creates also a
kcontrol whenever a jack input device is created. How recent is your

> Would it make sense to add support for JackName in ALSA? (Even though I
> understood it is somewhat deprecated and using input devices may lead to right
> issues.)

In a typical configuration input devices can be accessed only by root,
and PulseAudio runs as a normal user. Do you have a non-typical setup
where an input device could be used by PulseAudio?

AFAIK, it has been agreed that the kernel should always provide
kcontrols for jacks. Fixing the kernel seems like the right thing to
do, instead of working around kernel issues in PulseAudio.

> However, plug-in/out events can lead to some controls to be toggled by the
> kernel driver. Would it make sense, would it work and would it be a good idea to
> use them for the "JackControl" property?

Maybe? I don't really know.


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