[pulseaudio-discuss] [PATCH 2/2] alsa-mixer: Ignore some elements in the analog-output path

[David Henningsson]

On 2014-08-20 12:17, Tanu Kaskinen wrote:
> On Tue, 2014-08-19 at 17:05 +0200, David Henningsson wrote:
>>
>> On 2014-08-19 12:09, Tanu Kaskinen wrote:
>>> On Tue, 2014-08-19 at 07:47 +0200, David Henningsson wrote:
>>>>
>>>> On 2014-08-17 13:52, Tanu Kaskinen wrote:
>>>>> The analog-output path should be suppressed when there are more
>>>>> specific paths available. Currently that usually doesn't happen. The
>>>>> suppression can be done with the path subset detection, and this patch
>>>>> makes that work (another approach would be to mark the elements as
>>>>> required-absent, like analog-input does, but I like the subset
>>>>> suppression more, because it requires less stuff in the configuration
>>>>> files). The problem with listing the now-removed elements in
>>>>> analog-output.conf was that if the sound card had e.g. a Speaker
>>>>> element, then the switch behaviour was different between analog-output
>>>>> and analog-output-speakers, so analog-output was not considered a
>>>>> subset of analog-output-speakers.
>>>>
>>>> Removing the "Jack" ones should be okay, because they're required-any in
>>>> lineout.conf, so if these elements exist, there is always a "Line Out".
>>>>
>>>> I'm not sure about removing the elements. Could there be hardware where
>>>> we don't have anything making analog-output-speaker.conf show up, and we
>>>> still want the control over the things you remove below in
>>>> analog-output.conf?
>>>
>>> Could you be more specific? If there's nothing that makes
>>> analog-output-speaker show up, then which of these do you think we might
>>> want to control in analog-output: "Line HP Swap",
>>
>> Apparently added by myself in 2011, for a reason (needed by Dove
>> boards). So removing this one will regress that board. This one is quite
>> unusual so I bet keeping it wouldn't cause any unnecessary duplicates I
>> think.
>
> Can you elaborate, what regression will there be? It appears that "Line
> HP Swap" is needed for selecting between headphones and line-out. "Line
> HP Swap" isn't marked as "required-any" for analog-output-headphones or
> analog-output-lineout[1], but I'd guess that those Dove boards will have
> other elements that make analog-output-headphones and
> analog-output-lineout appear. And if analog-output-headphones and/or
> analog-output-lineout are available, then analog-output should be
> suppressed.
>
> [1] As I said in an earlier mail, I think analog-output-headphones and
> analog-output-lineout should mark "Line HP Swap" as "required-any". The
> reason is that even if that change doesn't make any difference in
> practice, in the theoretical case that no other elements exists but
> "Line HP Swap", the presence of that element signals that there are
> headphones and line-out outputs, otherwise there would be nothing to
> swap.

Looking at the alsa-info for the dove board [2], I also think "Line HP 
Swap" should be required-any for analog-output-headphones and 
analog-output-lineout. If you do so, it's okay to remove it from 
analog-output.

>>> "Headphone",
>>> "Headphone2",
>>
>> Arun changed the behaviour of these in 2013, before they behaved the
>> same. I'm not really sure what to do here. It seems reasonable to keep
>> them enabled for analog-output and muted for analog-output-speaker.
>
> "Headphone" is a "required-any" element for analog-output-headphones, so
> if the element exists, then analog-output-headphone is available, and
> analog-output should be suppressed. Same thing with "Headphone2".
>
>>> "Desktop Speaker"?
>>
>> AFAICR, I've never seen "Desktop Speaker". I think we can synchronise
>> the behavior so that it is the same on "analog-output" and
>> "analog-output-speaker".
>
> My patch is made with the assumption that analog-output should be
> suppressed always when there there are more specific paths available,
> with the exception of analog-output-mono (the patch removes also the
> "Master Mono" element from analog-output, but as I said earlier, that
> was a mistake). Based on this discussion, it seems that you either
> disagree with that basic assumption, or weren't properly aware of that
> assumption. If you think that the assumption is bad, I'd like you to
> give an example where that assumption causes breakage.

The question is if there ever can be the combination of e g 
analog-output-headphones and analog-output, when analog-output is 
controlling something we did not foresee, but still might be useful to 
control.
But since I was unable to come up with a good example, feel free to go 
ahead and remove the two headphone elements and sync Desktop Speaker 
with analog-output-speaker.


-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic

[2] https://launchpadlibrarian.net/33800317/alsa-info.txt.Z7Ddd7CdSl