Re: [RFC PATCH] docs: sound: kernel-api: writing-an-alsa-driver.rst: add FIXMEs

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

On Thu, Apr 20, 2023 at 04:27:35PM +0200, Takashi Iwai wrote:
>But why this has to be buried in the middle of a patch containing lots
>of other changes...?  Better to split out and start a new thread.
>
this "patch" doesn't contain any changes, only a bunch of questions.  
given the expected audience, i don't think that "burying" it was 
detrimental.

>IIRC, this was a result after struggles with the structured control
>implementations.  It became too complex, and the plain array with
>string representation can cover all complexity, while it still allows
>the grouping in user-space side.
>
i can see how a keyword based interface description is appealing - it 
keeps the kernel interface slim and flexible. but of course that comes 
at a steep cost in user space - i for one got completely lost and was 
unable to debug the bug described in the OP.
maybe a middle way would have been the best option?

>Again, the choice was done in a quarter century ago, and if you change
>it, you'll certainly break the whole things badly.  We must keep the
>compatibility.
>
i don't intend to actually change it. but suppose we did.

i suppose we'd have to add SNDRV_CTL_ELEM_ACCESS_{PLAYBACK,CAPTURE}.  
both could be set for unspecific and actually bidirectional controls. if 
neither is set, user space would fall back to the keyword based rules 
(and exceptions ...) - that would be backwards compatible and would 
enable a gradual migration.

regards