[pulseaudio-discuss] [PATCH] alsa: make headset-mic scanned earlier than headphone-mic

[Tanu Kaskinen]

On Tue, 2017-05-23 at 17:36 +0800, Hui Wang wrote:
> On 05/23/2017 04:20 PM, Tanu Kaskinen wrote:
> > On Tue, 2017-05-23 at 11:04 +0800, Hui Wang wrote:
> > > On 05/20/2017 10:51 PM, Tanu Kaskinen wrote:
> > > > On Fri, 2017-05-19 at 09:29 +0800, Hui Wang wrote:
> > > > > Hello Tanu,
> > > > > 
> > > > > Could you please help take a look at this patch? This patch really fix
> > > > > an issue on some Dell machines (with realtek codec and has no internal
> > > > > microphone on them), And I think this minor change will not introduce
> > > > > regression, it is pretty safe.
> > > > 
> > > > The patch only changes the order in which headset-mic and headphone-mic
> > > > are listed, and that order should not have any real impact on anything.
> > > > There's clearly a bug somewhere, but the bug can't be that the paths
> > > > are listed in the wrong order, since the order should not matter.
> > > 
> > > Yes, you are right. In theory, the headset-mic and headphone-mic have
> > > the same priority, so exchanging their order should not have any real
> > > impact on anything.
> > > 
> > > But in practice, this bug exposes that in some situation( when there are
> > > only headphone-mic and headset-mic, and neither of them is plugged in.),
> > > the headphone-mic is not suitable to be the default active_port.  So do
> > > you think if it is acceptable that I don't exchange their order, I just
> > > adjust their priorities to make the headset-mic's priority a bit higher
> > > than headphone-mic's?
> > 
> > If I understand correctly, headphones and headsets only work with the
> > headset-mic port, and microphones only work with the headphone-mic
> > port. Since it's more likely that a user plugs in headphones or a
> > headset than a microphone, I think it's ok to make the headset-mic
> > priority a bit higher than headphone-mic.
> 
> There is only one audio jack, users can plug headphone, headset or 
> microphone into it.  On some Dell machines which has realtek codec, the 
> codec/audio jack can't distinguish from hardware perspective what 
> devices the user plugged in, so users need to do a choice from UI program:
> 
> When user plug in a headphone and select the headphone,  the UI program 
> will set the headphone to be the active_port of pa_sink, and kernel 
> audio driver (patch_reaktek) will configure the codec to make that audio 
> jack work as a headphone jack

What makes the kernel do that? Does the kernel rely only on the mixer
settings set by pulseaudio to figure out how to configure the jack?
Which mixer elements affect the kernel's decision?

> When user plug in a headset and select the headset-mic, the UI program 
> will set the headphone to be the active_port of pa_sink and set the 
> headset-mic to be the active_port of pa_source,  and kernel driver will 
> configure the audio jack to be the headset jack
> 
> 
> When user plug in a microphone and select the headphone-mic, the UI 
> program will set the headphone-mic to be the active_port of pa_source, 
> and kernel driver will configure the audio jack to be the microphone 
> jack, then this jack can't work with headphone.
> 
> > 
> > However, that still doesn't fix the bug properly, I think. What if the
> > user plugs in a microphone and selects it in the UI? What will make
> > pulseaudio switch to the headphone-mic?
> 
> The UI program will do that. The UI program will call 
> pa_context_set_source_port_by_index() to do that.
> >   What will make pulseaudio
> > switch to the headset-mic port if headphones or a headset is plugged in
> > later?
> 
> This problem does not exist, since there is only one physical jack, if 
> user want to plug headset or headphone, he need to unplug the microphone 
> first. After user plug in the headphone or headset, the UI program will 
> call pa_context_set_source/sink_port_by_index() to set active port 
> according to user's choice.

But isn't it so that if the user selects headphones, the UI program
won't change the source port? So if the user first had a microphone
plugged in, and then unplugged that and plugged in headphones instead,
the headphones won't work, because the headphone-mic port is still
active.

-- 
Tanu

https://www.patreon.com/tanuk