[alsa-devel] [PATCH 0/3] ASoC: DPCM can care FE/BE merged format

[Kuninori Morimoto]

Hi Mark

> > 	unsigned int dpcm_merged_foramt:1;
> 
> Note that you've misspelt this - should be "format".

Ahh.. will fix in v2

> > I think we don't need flag control, but should I ?
> > (many other options are same style in struct snd_soc_dai_link)
> 
> Not quite sure what "flag control" is here, sorry?

Sorry for my confusable words.
Takashi mentioned

	>     .dpcm_merged_foramt
	>     .dpcm_merged_rate
	>     .dpcm_merged_chan

	Better to have bit flags.

I guess Takashi means like this

	u32 xxx_flags
	#define DPCM_xxxx_FORMAT	(1 << 0)
	#define DPCM_xxxx_RATE		(1 << 1)
	#define DPCM_xxxx_CHAN		(1 << 2)

But, this .dpcm_merged_xxx is defined as

	unsigned int dpcm_merged_foramt:1;

"flag control" here means #defined DPCM_xxxx_CHAN flag,
and I think we don't need it.

> > > > There are indeed cases where a BE takes incompatible hw configuration,
> > > > which needs be_hw_params_fixup.  But, in general, the FE's hw_params
> > > > is just copied to BE.  That is, we assume here blindly that FE's
> > > > configuration is compatible with BE's.  And, now this assumption isn't
> > > > true in rcar's case, so we face the issue.
> 
> > > Well, it's as much that we're assuming there's rewriting going on which
> > > handles things - in many of these systems everything will be going
> > > through a DSP which rewrites everything on the way.
> 
> > I guess we can use .be_hw_params_fixup if it is
> > "special rewrite" (ex 48kHz -> 44.1kHz, 8ch -> 2ch etc...).
> > But like this case (= it needs rewrite but normally we assume it)
> > using general method is useful.
> 
> > I'm happy to create/send v2 patch, but, it will be "flag" fixup ?
> 
> I'm having a bit of a hard time following, sorry.  If what you're saying
> here is that if we have a fixup method we should by default assume that
> only the front end constraints are relevant and ignore the back end then
> that does actually seem reasonable.

Yes it is !!

Best regards
---
Kuninori Morimoto