help understanding sound/snd_hda on mac pro w/ -STABLE.

Alexander Motin mav at
Tue Sep 9 09:32:49 UTC 2008

George Hartzell wrote:
> swell.k at writes:
>  > George Hartzell <hartzell at> writes:
>  > 
>  > [...]
>  > > An even simpler question would be, how can I test the other pcm
>  > > devices?
>  > 
>  > If you look closely at /dev/sndstat output you'll notice there is
>  > `default' keyword on one of the pcm's. To change it you have to
>  > set hw.snd.default_unit accordingly. It's documented in sound(4).
>  > Next time you'll run mpg123 it will use different /dev/dsp.
> bingo, at least a little bit with Alexander's 20080905 patch.
> With hint.hdac.0.config="gpio1" in /boot/device.hints and
> hw.snd.default_unit="2" I can use mpg123 to play sound out of the
> line-out jack in the back of the unit.
> I've tried combinations of gpio0, gpio1, gpio2 and default_unit's of
> 0,1,2,3 and can't get sound out of the headphone jack on the front of
> the machine.
> Thanks for the patch and the help understanding what's going on!

As I see from 20080812 dmesg output - it routes all output pins to the
same DAC. It was surely a bug, so it was fixed in next version. The only
case to use same DAC is Headphone redirection.

I don't see any reason why playing via dsp0/1/2/3 should not play via
all of your connectors. Try to play more with GPIOs and make sure to set
all control to 100% in all your mixers (/dev/mixer0/1/2/3). This codec
supports -64/+0dB volume control range and even pcm=75 and vol=75 may be
too quiet for it as driver uses logarithmic scale of the codec.

Alexander Motin

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