ALSA: pcm: add comment warning that SNDRV_PCM_RATE_* bits are ABI

[marc-hb]

Add a comment warning that SNDRV_PCM_RATE_* were copied in 2017 to alsa-lib file "tplg_local.h" which makes them an ABI now.

Pure comment fix, no code change.

Link: #4966

[marc-hb]

For convenience: alsa-project/alsa-lib@c550a421a3

[dbaluta]

Looks good to me! This should be merged directly via Mark Brown's tree and then cherry-picked (or rebased) back here.

[plbossart]

let's ask @tiwai for his advice/comments

[tiwai]

Maybe it'd be clearer to move it to uapi/sound/asound.h, as an official part of uapi?

[marc-hb]

Maybe it'd be clearer to move it to uapi/sound/asound.h, as an official part of uapi?

Anyone else agrees or disagrees? This was supposed to be a "quick doc fix" but it's been 5 days now so if it's significantly more complicated than expected then I will just close it.

[dbaluta]

Maybe it'd be clearer to move it to uapi/sound/asound.h, as an official part of uapi?

Anyone else agrees or disagrees? This was supposed to be a "quick doc fix" but it's been 5 days now so if it's significantly more complicated than expected then I will just close it.

Do you mean to move all SNDRV_PCM_RATE_* to uapi/sound/asound.h? This should be fine then remove it from "tplg_local.h"

[marc-hb]

Let's be realistic: I'm not going to have the time to do any of this any time soon.