Subject: [RFC PATCH v4 3/8] staging: imx-drm: Document updated imx-drm device tree bindings

From: [email-masked] (Tomi Valkeinen)
Date: Thu, 27 Feb 2014 13:06:52 +0200

On 25/02/14 16:23, Philipp Zabel wrote:

> +Freescale i.MX DRM master device
> +================================
> +
> +The freescale i.MX DRM master device is a virtual device needed to list all
> +IPU or other display interface nodes that comprise the graphics subsystem.
> +
> +Required properties:
> +- compatible: Should be "fsl,imx-drm"
> +- ports: Should contain a list of phandles pointing to display interface ports
> +  of IPU devices
> +
> +example:
> +
> +imx-drm {
> +	compatible = "fsl,imx-drm";
> +	ports = <&ipu_di0>;
> +};

I'm not a fan of having non-hardware related things in the DT data.
Especially if it makes direct references to our SW, in this case DRM.
There's no DRM on the board. I wanted to avoid all that with OMAP
display bindings.

Is there even need for such a master device? You can find all the
connected display devices from any single display device, by just
following the endpoint links.

>  display at di0 {
>  	compatible = "fsl,imx-parallel-display";
>  	edid = [edid-data];
> -	crtc = <&ipu 0>;
>  	interface-pix-fmt = "rgb24";
> +
> +	port {
> +		display_in: endpoint {
> +			remote-endpoint = <&ipu_di0_disp0>;
> +		};
> +	};
>  };

Shouldn't the pix-fmt be defined in the endpoint node? It is about pixel
format for a particular endpoint, isn't it?

> diff --git a/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt b/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt
> index ed93778..578a1fc 100644
> --- a/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt
> +++ b/Documentation/devicetree/bindings/staging/imx-drm/ldb.txt
> @@ -50,12 +50,14 @@ have a look at Documentation/devicetree/bindings/video/display-timing.txt.
>  
>  Required properties:
>   - reg : should be <0> or <1>
> - - crtcs : a list of phandles with index pointing to the IPU display interfaces
> -           that can be used as video source for this channel.
>   - fsl,data-mapping : should be "spwg" or "jeida"
>                        This describes how the color bits are laid out in the
>                        serialized LVDS signal.
>   - fsl,data-width : should be <18> or <24>
> + - port: A port node with endpoint definitions as defined in
> +   Documentation/devicetree/bindings/media/video-interfaces.txt.
> +   On i.MX6, there should be four ports (port@[0-3]) that correspond
> +   to the four LVDS multiplexer inputs.

Is the ldb something that's on the imx SoC?

Do you have a public branch somewhere? It'd be easier to look at the
final result, as I'm not familiar with imx.

 Tomi

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