On 08/22/2013 05:40 AM, Nicolin Chen wrote:

Hi Stephen,

On Wed, Aug 21, 2013 at 12:30:59PM -0600, Stephen Warren wrote:

quoted

I still don't think those two properties are correct.

Exactly what node will those phandles point at?

There definitely should not be a DT node for any "dummy CODEC",
irrespective of whether this binding calls the other node a "CODEC" or a
"dummy CODEC".

If these properties are to contain phandles, it would be acceptable for
the referenced node to be:

* A node representing the physical connector/jack on the board.

* A node representing some other IP block on the board, such as an HDMI
encoder/display-controller

I think those options are unlikely in general, so I think instead these
properties should just be Boolean indicating that "something" is
connector to the S/PDIF RX/TX, without specifying what that "something"
is. It doesn't matter what at least in the connector/jack case, although
perhaps it does in the HDMI encoder/display-controller?

Documentation/devicetree/bindings/sound/spdif-receiver.txt
If I understand correctly, this doc for the dummy codec should be invalid?

Yes, I'm not convinced that binding is a good idea; it describes
something that often doesn't actually exist in HW. (Sometimes there's a
real S/PDIF receiving device on board, but sometimes there's nothing
except a jack/connector).

It'd be useful if other DT binding maintainers could weigh in on this to
confirm/deny my thoughts.

But this patch, the spdif machine driver, is based on this codec driver,
pls check the following code:

164 +       codec_rx_np = of_parse_phandle(np, "spdif-receiver", 0);
165 +       if (codec_rx_np) {
169 +               data->dai[num_links].codec_of_node = codec_rx_np;
173 +       }

Accordingly, the binding I planned to add in DT:

27 +       spdif_rx_codec: spdif-receiver {
28 +               compatible = "linux,spdif-dir";
29 +       };
30 +
31 +       sound-spdif {
32 +               compatible = "fsl,imx-audio-spdif",
33 +                          "fsl,imx-sabreauto-spdif";
34 +               model = "imx-spdif";
35 +               spdif-controller = <&spdif>;
37 +               spdif-receiver = <&spdif_rx_codec>;
38 +       };

So if the DT can't allow me to include this codec node, how could I
handle it in the current baseline.

I would expect the machine driver's probe routine to create the dummy
S/PDIF receiver object itself, and register it by calling
snd_soc_register_codec(). That way, only the machine driver code need
know it (dummy CODEC) exists.