Re: [PATCH v7 2/2] ASoC: fsl: Add S/PDIF machine driver

Am Montag, den 19.08.2013, 11:01 +0100 schrieb Mark Rutland:

On Mon, Aug 19, 2013 at 10:50:43AM +0100, Nicolin Chen wrote:

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Hi,

On Mon, Aug 19, 2013 at 10:24:58AM +0100, Mark Rutland wrote:

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Is this used semantically, or is it a completely arbitrary string?  In
either case I don't see why the compatible string doesn't give the
driver enough to have a sensible value.

I'm confused as to why we need this. The phrase "user-visible" in a
device description seems very odd.

The string would be in the ALSA device list:
ALSA device list:
  #0: imx-spdif

I think it can be a sort of arbitrary as long as users know which this 
device exactly is when they catch the name by 'aplay -l' or 'arecord -l'

The phrase "user-visible" is being used in many current docs, I don't 
dare to change it unless a sage gives me a suggestion.

I can see that there is entrenched usage, but this really seems to be
embedding Linux-specific implementation details into the dt. I don't see
why the driver cannot select a sensible name, but perhaps I'm missing
something.

Mark, is there any reason we need to handle the user-visible name of the
device this way?

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+
+  - spdif-controller : The phandle of the i.MX S/PDIF controller
+
+
+Optional properties:
+
+  - spdif-transmitter : The phandle of the spdif-transmitter dummy codec
+
+  - spdif-receiver : The phandle of the spdif-receiver dummy codec
+
+* Note: At least one of these two properties should be set in the DT binding.

Are all four units (comlpex,controller,transmitter,receiver) really
separate blocks?

At least they are separate drivers as I mentioned in the commit comments.

I'm not sure that the boundary of Linux drivers should necessarily
determine the way we carve up the description of IP blocks, though
presumably it's a pretty sensible way of carving it up or we wouldn't
have done it.

The transmitter and receiver can be real external codec devices with
S/PDIF input or output pads connected to the i.MX S/PDIF. One example
would be the Analog Devices ADV7612 HDMI receiver, which can output
audio taken from HDMI input via S/PDIF (just as via I2S).

The dummy codec devices are just needed if the S/PDIF pads are directly
routed to externally accessible connectors.

regards
Philipp