Re: [PATCH] ALSA: emu10k1: fix multi-channel playback device class

[Oswald Buddenhagen <oswald.buddenhagen@gmx.de>]

On Sun, Apr 23, 2023 at 09:30:11AM +0200, Takashi Iwai wrote:
>On Sat, 22 Apr 2023 18:10:21 +0200,
>Oswald Buddenhagen wrote:
>> 
>> It's multi, not mono/stereo.
>> 
>> AFAICT, this doesn't do anything in the kernel.
>
>... but those values are read by user-space.
>
>> Also, I think the subclass is meaningless for devices with just one
>> stream, but whatever.
>
>Again, the value is read by user-space.
>
i assumed that much.
but these are another thing that appears to have exactly zero useful 
documentation.

>So changing both have clear influence on the user-space program, and
>unless you have to change this for fixing a real bug (and there is no
>other way), this is too risky.  IOW, too late to change, we have to
>accept those values.
>
there aren't any precedents for use of SNDRV_PCM_CLASS_MULTI and 
SNDRV_PCM_SUBCLASS_MULTI_MIX in the kernel tree.
there don't appear to be relevant hits outside the kernel, either.
it's conceivable that some code would check for the *_GENERIC enums, but 
i didn't find such code.
so i'd postulate that these enums are effectively dead, and both the 
risk and the gain of this change are about zero.
i suggest to initiate a formal deprecation procedure for the MULTI enum 
values, however that's supposed to look like.

regards