Re: [PATCH 4/9] Doc/DT: Add DT binding documentation for HDMI Connector

On Fri, Feb 28, 2014 at 06:15:05PM +0200, Tomi Valkeinen wrote:

On 28/02/14 18:06, Russell King - ARM Linux wrote:

quoted

quoted

+hdmi0: connector@1 {
+	compatible = "hdmi-connector";
+	label = "hdmi";
+
+	hdmi_connector_in: endpoint {
+		remote-endpoint = <&tpd12s015_out>;
+	};
+};

It seems rather weird to have DVI connectors having an optional I2C
property, but HDMI (which augments DVI) not having that as at least an
optional property.

I have added only the properties that I have used. I did think about the
i2c for HDMI also, but thought that I don't use it, and so can't test
it, and so I could well create a bad binding.

And, as I don't see any issue in adding it later, when someone uses it,
I decided to leave it out.

quoted

I can quite well see the iMX HDMI support needing an i2c bus here.

Also, HDMI has two connector standards - type A and type B, much like
the single vs dual link of DVI.  Again, DRM exposes this to userspace.

True, but isn't that just a form factor? No functional differences? But
I agree, we can add the two types here also to the compatible string.

HDMI A is 19 pins carrying TMDS channels 0-2.  HDMI B is 29 pins
carrying TMDS channels 0-5.  So, the difference is the same as the
single vs dual link on DVI-D/I connectors.

There's actually three HDMI connectors:

  All three connectors carry all required HDMI signals, including a TMDS
  link. The Type B connector is slightly larger and carries a second TMDS
  link, which is necessary to support very high resolution displays using
  dual link. The Type C connector carries the same signals as the Type A
  but is more compact and intended for mobile applications.

So, Type C and Type A are electrically the same.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.