[pulseaudio-discuss] Configuring alsa mixers in the "off" profile.

[Matti J. Aaltonen]

On 10/06/2011 04:22 PM, Matti J. Aaltonen wrote:
> On 10/06/2011 01:55 PM, ext Mark Brown wrote:
>> On Thu, Oct 06, 2011 at 01:49:38PM +0300, Tanu Kaskinen wrote:
>>
>>>> Yeah the driver is unable to detect directly if someone wants to use
>>>> the analog signal. But that's not a big problem, there still could
>>>> exist the facility for explicitly turning the radio on and off. It's
>>>> also possible to imagine a use case where only RDS data is of
>>>> interest.
>>> arguing for or against turning off the radio automatically? What do you
>>> mean by "that's not a big problem"? (That's the sentence that causes my
>>> confusion.) If the driver doesn't know if someone is using the analog
>>> output (or RDS), isn't that a showstopper, if the goal is to turn off
>>> the radio automatically without any explicit request?
>> The driver can easily find this information out for the audio, there's
>> power information available from the audio subsystem.  I'd assume the
>> RDS can do the same thing easily by looking to see if the relevant
>> device is open or whatever.
>
> Yes RDS is not a problem as there are read and write functions that 
> can be used to turn the device on. I just meant that it needs to be 
> implemented separately.
>
> But the handling of the analog audio isn't that straightforward, or 
> maybe it is... I'm not familiar with pulse audio.
> Earlier versions of lankku had analog audio output connected to the 
> headphone amplifier, turning that amp on could also turn on the radio. 
> But that amplifier could be turned on for other reasons as well. How 
> to identify that it is to be used to amplify the signal from the 
> radio... Also are "we" trying to find a solution for a particular use 
> case (xxxxx doesn't have analog audio possibility for the radio) or an 
> up-streamable more general solution?

There could be a function in the board file that the driver could poll 
to see if you need to turn the radio on. But if you have on multipurpose 
analog amplifier
with inputs simply soldered together you still have a difficult 
situation. But if you have an easy solution to this that if of course great.