[CentOS] Mate and USB headphones

[Alice Wonder]

On 01/07/2017 03:34 PM, Fred Smith wrote:
> On Sat, Jan 07, 2017 at 02:11:47PM -0800, Alice Wonder wrote:
>> On 01/07/2017 01:42 PM, Laurent CREPET wrote:
>>> On Sat, Jan 7, 2017 at 10:23 PM, Alice Wonder <alice at domblogger.net> wrote:
>>>
>>>> Logitech H540 headphones were working fine.
>>>>
>>>> Suddenly stopped.
>
> On my C7 Mate system I have what may be the same issue:
> if the "sound preferences" app (aka Mate Volume Control) is already
> running at the time the USB headphones are plugged in, the USB phones
> appear as disabled.
>
> OTOH, if the phones are plugged in, then the Mate Volume Control is
> started, they are not listed as disabled.

I leave the headphones plugged in all the time, they were working fine 
and just recently stopped after doing some work in Audacity, I am 
wondering if Audacity disabled them for some reason but if it did, not 
while I was using it.

I'm at a loss as to what triggered them to be listed as disabled.

>
> When that first began happening (a year or two ago, I think) I
> posted on the Mate forums and someone said he thought he saw the
> bug and would do a build to fix it.  unfortunately his build did not
> fix it, and it has remained.
>
> AFAIK, I have no sound hardware blacklisted (where do you blacklist it?)
> I have an Nvidia card with HDMI output, and it shows up in the sound
> app, but since I don't do HDMI video on this machine I always just
> ignore that device.

Blacklist is in /etc/modprobe.d/blacklist.conf

On mine it consists of

blacklist snd_hda_intel
blacklist snd_hda_codec_hdmi

I think only the first is necessary to prevent the useless sound chip 
from being chosen but I have both lines there.