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!