[alsa-devel] Quirk to disable master volume control in PCM2702

Clemens Ladisch clemens at ladisch.de
Tue Nov 17 10:04:30 CET 2009

Javier Kohen wrote:
> I've written the attached patch to disable the master volume control
> in this chipset. The datasheet [1] documents two independent channel
> volume controls, one master mute control and one master volume
> control. However, at least on my device (a Fubar USB DAC), the master
> volume control always returns USB stalls when queried for any of its
> parameters (min/max/res/cur).

I'd guess that Windows ignores the master volume when it finds
channel volume controls, so this function was never actually tested.

> However, it seems that either the USB specs are wrong,

They are abominations written by committees.

> or my USB hub or the card are buggy.

Your hub is certainly buggy ...

> the PCM2702 and my motherboard don't interact well. After a while the
> sound is degraded, first into a hiss, then into pure noise.

... the card too.

Your patch looks good; please provide a log message and a Signed-off-by

Best regards,

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