[alsa-devel] [PATCH] New quirk for USB DAC 08bb:2704

[Omari Stephens]

On 02/14/2011 05:10 PM, Takashi Iwai wrote:
> At Sat, 12 Feb 2011 22:53:25 +0000,
> Omari Stephens wrote:
>>
>> Howdy, all
>>
>> I have one of these:
>> http://www.chordelectronics.co.uk/products_detail.asp?id=63
>>
>> It's got one of these USB DACs inside
>> ID 08bb:2704 Texas Instruments Japan
>>
>> The DAC has a single mixer control, Master, which allows you to adjust
>> volume and mute/unmute.  The fun thing is that the volume adjustment has
>> no effect whatsoever.  On machines running pulse, this means that output
>> will be at 0dB pretty much all the time.  (Of course, this is true of
>> non-pulse machines also).
>>
>> The attached patch disables the Master control, which causes pulse to
>> control levels entirely in software, as it should for this device.
>>
>> The main downside to this patch is that, while the volume part of the
>> Master control is non-functional, the mute/unmute aspect does work as
>> expected.  I couldn't figure out how to change the Master control to
>> just a mute/unmute control, but if someone has suggestions on what to
>> do, that'd be appreciated.  Judging by the comments in the code (and
>> contrary to what I wrote in the map comment), I presume the mute/unmute
>> control is the only reason why 08bb:2702 isn't doing this same thing.
>
> The patch looks good to me.  Could you give your sign-off?
Oops; sorry (haven't submitted a kernel patch before).  Will do.

That said, I have some friends with the same device, and at least one 
says that the volume control works fine for him, so I want to do a bit 
more investigation before this quirk gets added.  Will send email when I 
get things figured out a little more.

--xsdg