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

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

On Fri, Apr 21, 2023 at 10:55:23AM +0200, Takashi Iwai wrote:
>> 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.
>
>The backward compatibility isn't really easy as you wrote, I'm
>afraid.  If you run an old user-space stuff on the new kernel, you
>must not fill that new information bit but translate it to the string
>suffix instead; and that has to be done inside the kernel
>automagically.
>
right, i didn't mention it, but i imagined the strings to remain the 
same, both for backwards compat, and because they serve a "label" 
function regardless of semantic interpretation. of course that would 
make them partially redundant with the newly added bits, but that 
doesn't seem too bad to me.

anyway, i think i have enough background info now to write a nice 
paragraph for the docu.

thanks!