[pulseaudio-discuss] [PATCH] alsa: don't assume that hw:x is an analog output

[Takashi Iwai]

On Sat, 29 Apr 2017 14:45:41 +0200,
Arun Raghavan wrote:
> 
> (looping in Takashi for his thoughts, since we'd discussed this a long
> time ago)
> 
> On Fri, 28 Apr 2017, at 12:38 AM, Tanu Kaskinen wrote:
> > On Wed, 2017-04-26 at 14:19 +0530, Arun Raghavan wrote:
> > > On Mon, 24 Apr 2017, at 08:36 PM, Tanu Kaskinen wrote:
> > > > Previously, if front:x didn't work, we would try to use hw:x for analog
> > > > stereo output. There's no guarantee that hw:x is an analog output,
> > > > however. For example, the Intel HDMI LPE driver uses hw:x for HDMI
> > > > output, and PulseAudio incorrectly created analog profiles for that
> > > > card, because front:x doesn't work but hw:x does.
> > > > 
> > > > This patch changes things so that the analog stereo mapping doesn't any
> > > > more use hw:x as a fallback. A separate "unknown stereo" fallback
> > > > mapping is added to handle the rare case where hw:x is the only PCM
> > > > device that works.
> > > > 
> > > > BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=100488
> > > > ---
> > > 
> > > I recall that front: actually adds a softvol on top of hw: (in some
> > > cases?), and we actually wanted to move to hw: always.
> > 
> > Using hw: always seems like a bad idea (for the reasons described in
> > this patch).
> > 
> > > Do we know if that's still true?
> > 
> > At least I don't know.

The softvol is skipped by passing SND_PCM_NO_SOFTVOL bit flag at
opening a stream even if softvol is included in the configuration.
IIRC, this was introduced exactly for PA :)


Takashi