[pulseaudio-discuss] [PATCH] suspend-on-idle: Allow disabling suspending for specific devices

[Arun Raghavan]

On Fri, 2013-09-13 at 05:52 -0400, David Henningsson wrote:
> 2013-09-13 04:00, Tanu Kaskinen skrev:
> > On Fri, 2013-09-13 at 13:20 +0530, Arun Raghavan wrote:
> >> On Fri, 2013-08-30 at 15:11 +0200, David Henningsson wrote:
> >>> On 08/30/2013 09:28 AM, Tanu Kaskinen wrote:
> >>>> On Fri, 2013-08-30 at 08:16 +0200, David Henningsson wrote:
> >>>>> On 08/29/2013 04:36 PM, Tanu Kaskinen wrote:
> >>>>>> Sometimes it would be nice to disable module-suspend-on-idle for
> >>>>>> specific devices. For me the use case is to keep a HDMI sink running
> >>>>>> all the time to avoid loss of audio when starting to play a stream to
> >>>>>> the device (the HDMI receiver eats a bit from the beginning of the
> >>>>>> stream when the device is opened). This is arguably a hacky solution
> >>>>>> to the problem, but on the other hand, I think it's very sensible to
> >>>>>> interpret negative timeout in the module-suspend-on-idle.timeout
> >>>>>> property as disabling the suspending altogher. This is also how the
> >>>>>> exit-idle-time configuration option behaves (negative value disables
> >>>>>> automatic exiting).
> >>>>> Didn't Arun have another solution for a similar problem? Like a sink
> >>>>> ALWAYS_RUNNING flag or something.
> >>>> Yes, he did. That patch was not merged, and I don't know if Arun plans
> >>>> to still work on it.
> >>>>
> >>>> Regardless of Arun's solution, I think it makes sense to support
> >>>> negative value for the module-suspend-on-idle.timeout property to be
> >>>> consistent with other timeout parameters.
> >>>>
> >>> Hmm, it looks like there already is a module-suspend-on-idle.timeout
> >>> property and you're just improving its functionality. Then I would
> >>> typically prefer this over a new sink flag.
> >>>
> >>> Even better if the module-suspend-on-idle.timeout was documented though...
> >>>
> >>> Arun, would this solve your problem as well? Would it be possible for
> >>> the two of you to synchronise your efforts?
> >> Tanu and I discussed this on IRC. I don't think we should use this
> >> property to do what I was trying to with ALWAYS_RUNNING - the module
> >> parameters is mechanism, and the always-running-ness is policy. Don't
> >> want to mix the two.
> >>
> >> That said, I've no objection to what the patch is trying to do, per se
> >> (i.e. extend/standardise the semantics of a device property that we
> >> already support).
> > OK, patch pushed.
> >
> > For the record, I agree with Arun in that this property shouldn't be
> > used in the hardware description files (UCM or alsa-mixer files). I
> > didn't quite understand Arun's explanation about mechanism vs. policy.
> > My reason for disliking the property is that it's specific to
> > module-suspend-on-idle, while "idle suspending not recommended" is a
> > hardware property that shouldn't be tied to any particular module.
> >
> 
> I can see your point, but I also like to be pragmatic - if we now have 
> this property tied to this module, and the module can achieve what Arun 
> needs, I wouldn't add another way of doing the same thing, unless it was 
> necessary. That just gives us additional code to maintain and test.

I disagree in this case, because it's a hack, but ...

> Not that I'm so strong about it that I want to block Arun's patch if he 
> really feels the need to add that flag in addition to this patch, it 
> just seems superfluous to me.

... in the specific case that I'm working with, I no longer need to open
modem PCMs in PulseAudio (pushed it to a separate process). Considering
that this keeps coming up, though, it would be nice to have a solution
available instead of starting this discussion all over again in a few
months.

Thoughts?

-- Arun