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

[Takashi Iwai]

At Tue, 21 Apr 2015 08:15:27 +0000,
Kuninori Morimoto wrote:
> 
> 
> Hi Takashi-san
> 
> Thank you for your feedback
> 
> > > These patches add new .dpcm_merged_foramt to merge FE/BE formats.
> > > It will be no sound if DPCM were below style, and user selects S24_LE.
> > > 
> > > 	FE: S16_LE/S24_LE
> > > 	BE: S16_LE
> > > 
> > > DPCM will selects FE/BE merged formats (= S16_LE here) if
> > > FE has .dpcm_merged_foramt.
> > 
> > Conceptually, you need to refine all FE hw_params with BE's, not only
> > formats.
> 
> Hmm...
> I think DPCM can rewrite all .hw_params,
> and basically it don't want to constrain with the BE constraints.

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.

> So, I thought we can have below for each purpose ?
> 
>     .dpcm_merged_foramt
>     .dpcm_merged_rate
>     .dpcm_merged_chan

Better to have bit flags.
 
> Maybe I'm misunderstanding, but if this feature
> refines above all hw_params, it will conflicts
> with .be_hw_params_fixup ?

Yeah, there it'll need to clear the flag.


thanks,

Takashi