On Wed, Aug 27, 2014 at 05:33:55PM -0700, Kuninori Morimoto wrote:

Now, my system is working well with simple-card by this

	sound {
		compatible = "simple-audio-card";
		...

		cpu {
			sound-dai = <&rcar_sound 0>;
		};
		codec {
			sound-dai = <&ak4643>;
		};
	};

The reason why I'm tring to support DPCM on simple-card is "sampling rate convert".
My rcar_sound can convert sampling rate, and I tried to add this feature as
rcar_sound property.
But, Mark rejected and requests me to use DPCM for it,
since it can be common featrue.
Current existing simple-card can't use it, and I'm tring.
But, am I misunderstanding ?

There's two separate things here.  One is how the code is implemented
(which does look very much like it should be doing DPCM) and the other
is how the DT binding looks - the DT binding is supposed to be a
hardware neutral thing and not depend on Linux implementation details.
If you've already got the hardware described well enough to discover
everything then that generally indicates that the DT binding should not
need to change.