Re: [PATCH v2 09/14] ASoC: audio-graph-card2: add Yaml Document

[Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>]

Hi Mark

Thank you for clearing the topics.
I think I could understand Rob and your expectation.

> It's more about making sure that new users that currently use
> simple-card are using audio-graph-card instead - we need to keep
> simple-card around for existing users (or at least the binding but
> probably it's more effort than it's worth to merge the binding parsing
> code elsewhere) but we should be avoiding adding new users of it.  I've
> been pushing people to use audio-graph-card for a while, TBH we should
> probably just go ahead and flag simple-card as deprecated in the binding
> now since I don't think there's any reason anyone is forced to use it at
> this point.
(snip)
> > > Why do we need these changes? I'm not wild about a new generic binding
> > > replacing an existing one which only has 2 or 3 users IIRC. Plus
> > > there's already the Renesas variant. (On the flip side, only a few
> > > users, easier to deprecate the old binding.)
> 
> > Sorry I don't understand
> > 	- Who is "2 or 3 users" ?
> 
> Just that there's not that many users of the existing audio-graph-card
> (though it's a bit more than 2 or 3 and it's newer stuff rather than
> old).
(snip)
> I think what Rob is looking for here is a more detailed description of
> what the problems are with the existing binding that require a new
> binding - what's driving these big changes?  TBH this is part of why
> I've been holding off on review, I need to get my head round why we
> can't fix the existing binding in place.

OK, let's cleanup the problem.

O : supported
- : not supported
x : Annotated

	simple-card
	 O: Normal connection
	 -: DPCM
	 -: Multi CPU/Codec
	 -: Codec2Codec

	audio-graph-card
(A)	 O: Normal connection
(B)	 x: DPCM
	 -: Multi CPU/Codec
	 -: Codec2Codec

	x: Tegra uses is as customize audio-graph-card

	audio-graph-card2
	 O: Normal connection
	 O: DPCM
	 O: Multi CPU/Codec
	 O: Codec2Codec

We need to keep simple-card, I think there is no discussion is needed here.

About audio-graph-card vs audio-graph-card2,
I think keeping (A) only on audio-graph-card2 is not super difficult
(But some message will be indicated. see below).
Supporting (B) on audio-graph-card2 is difficult.

I'm not sure detail, but we can do like this ?

	step 1)
	- add audio-graph-card2 which have (A) compatibility.
	- indicate "audio-graph-card will be deprecated" on audio-graph-card

	step 2)
	- Tegra switch to use audio-graph-card2
	- confirm that all existing audio-graph-card user have no problem on
	  audio-graph-card2 too.

	step 3)
	- remove audio-graph-card

My concerns are...

	- I'm not sure how DT is strict.
	  If we removed audio-graph-card, but user uses old Tegra DT on it...
	  We can't remove audio-graph-card forever if DT was super strict (?).

	- The naming of audio-graph-card vs audio-graph-card2 driver file.
	  because audio-graph-card will be removed later.

	- audio-graph-card2 can keep (A) compatible, but some features
	  are not recommended. Existing user will get such message.
	  And because of this compatibility, audio-graph-card2 can't remove
	  this "un-recommended" feature.

Thank you for your help !!

Best regards
---
Kuninori Morimoto