Headphone volume adjustment

[Mark Brown]

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.

> 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.

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.
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