Headphone volume adjustment

James Cameron quozl at laptop.org
Thu Aug 15 20:07:34 EDT 2013

On Fri, Aug 16, 2013 at 12:55:41AM +0100, Mark Brown wrote:
> On Fri, Aug 16, 2013 at 09:05:04AM +1000, James Cameron wrote:
> > On Thu, Aug 15, 2013 at 11:55:34PM +0100, Mark Brown wrote:
> > > End users aren't supposed to see the configuration, the system
> > > sound server is supposed to do that - there's some work going on
> > > to improve this in PulseAudio at the minute and there's a
> > > standard set of helpers in alsa-lib (UCM) which should help
> > > implement this for anything else.
> > We certainly don't use PulseAudio, and probably don't use UCM.
> I guess the Fedora installs will?  You'd have to try not to.  In
> general I'd recommend it for any use; it's really rather advanced in
> terms of features (I've not seen anything else that has the
> dynamically adjusted buffer sizes during playback) and does a great
> job of simplifying the system setup down for the applications.

Yes, we try not to.  I do not recall the technical arguments in full,
Daniel would, but they included very limited processing power, very
limited memory, it didn't work when we first tried it, and a suite of
applications that use the ALSA controls directly that we would have to

> > Therefore the number and type of controls exposed to user space
> > were actually quite important to us.  We have had bad experiences
> > with controls being set by uncontrolled applications, being saved
> > by alsactl for next boot, and resulting in laptops in the field
> > without working audio.  For many weeks during development and
> > board bringup the default controls didn't get us sound, but
> > developers with suitable saved controls had no trouble.  This
> > delayed us significantly, as test results could not be reproduced.
> Right, this is where not having use case management in your sound
> server tends to cause trouble - if your userspace just uses whatever
> happens to be lying around on the box and worse saves user settings
> then things are going to go wrong.  To be honest I'm surprised that
> there still aren't problems even with cutting down the number of
> controls, so long as there's any configurability people are going to
> be able to cause problems.

We handle the remaining controls manually in a startup script to
ensure their sanity.

> You're kind of not supposed to have working audio with the out of
> the box setup, or at least you're supposed to just have the default
> setup for the CODEC when tends to have everything off.


> > > There's some work going on on this upstream for PulseAudio, it
> > > might be good to
> > Your message ends abruptly at this point.
> Oops.  I think all I was going to say was something about checking
> in with them about what they're up to, it'd probably be useful to
> make sure that what they're doing plays nicely.


James Cameron

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