From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Gabriel M. Beddingfield" <gabrbedd@gmail.com>
Subject: Re: caiaq driver: audio 4 dj and jackd
Date: Wed, 04 Dec 2013 20:11:51 -0800
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To: Daniel Mack <daniel@zonque.org>
Cc: Alsa-devel <alsa-devel@alsa-project.org>, Antonio Ospite <ao2@amarulasolutions.com>
List-Id: alsa-devel@alsa-project.org

On 12/02/2013 08:00 AM, Daniel Mack wrote:
>>> Technically yes, but changing that would mean breakage for all other
>>> users, and making it configurable would result in yet another moving
>>> part which makes things even more complex.
>>
>> How would this cause breakage?  Users that use 2 stereo substreams could
>> still work normally.
>
> Yes, unless you opened the first subdevice with more than 2 channels.
> Then an existing user for the second stream breaks. IOW: the possible
> configuration and usage for subdevice 1 changes depending on that of
> subdevice 0.

Suppose a 2nd PCM device is added that would allow 1-4 channel 
playback/capture (call it "Multichannel Audio" or something).  This pcm1 
would be mutually exclusive with pcm0 (I.e. while one is open you can't 
use the other).

Existing applications using hw:n,0,0 and hw:n,0,1 see the exact same 
interface/behavior.  The only failure mode is if the multichannel PCM is 
in use.

Applications using multichannel work-flows would use hw:n,1.

While it's not a "just works" solution -- directing users to hw:n,1 is a 
whole lot better than teaching them how to set up a multi plugin.

-gabe