[pulseaudio-discuss] Changes to deal with modem PCMs

[Arun Raghavan]

On Mon, 2012-07-23 at 15:05 -0500, Pierre-Louis Bossart wrote:
> On 7/23/2012 3:57 AM, Arun Raghavan wrote:
> > Hello,
> > While discussion on how we should deal with hardware with different
> > requirements from standard desktop cases continues, I'd like to solve the
> > problem of having modem PCMs that we don't want to auto-suspend in the near
> > future. For this, I've attached a couple of patches that allow a sink or source
> > to be flagged as "always running" which would cause suspend to be avoided if
> > possible.
> >
> > Any objections?
> Yes. These devices are used to open connections to modems without 
> receiving any data from userspace.
> I don't think PulseAudio should flag specific sinks this way, somehow 
> the information should be available at the ALSA level that such devices 
> do not provide/expect any data and should not be suspended. This 
> information is available at the kernel level (no_pcm flag or something), 
> it should be made available to user-space.

In the patches I sent, the actually setting of the flag is not present.
I've got it included in my policy module, but it could easily be
signaled by the kernel as you suggest, or in UCM config.

Ideally, I'd use Tanu's suggestion to not expose the phone PCMs as sinks
at all, and just have them opened/closed in the alsa module (he suggests
an API to do this (pa_alsa_card_open_cellular_...), but I think we could
potentially just tie it to the "Voice Call" UCM verb). However, my fear
is that this is too specific to the OMAP4, which is why I went down this
route.

-- Arun