[PATCH 1/3] drm/exynos: add super device support

[Philipp Zabel]

Hi Inki,

Am Donnerstag, den 27.03.2014, 21:43 +0900 schrieb Inki Dae:
> This patch adds super device support to bind sub drivers
> using device tree.
> 
> For this, you should add a super device node to each machine dt files
> like belows,
> 
> In case of using MIPI-DSI,
> 	exynos-drm {
> 		compatible = "samsung,exynos-drm";
> 		crtcs = <&fimd>;
> 		connectors = <&dsi>;
> 	};

Russell had suggested a similar binding for i.MX, but we have since
changed it to look like this instead:

-	imx-drm {
-		compatible = "fsl,imx-drm";
-		crtcs = <&ipu 0>, <&ipu 1>;
-		connectors = <&hdmi>, <&ldb>;
-	};
+	display-subsystem {
+		compatible = "fsl,imx-display-subsystem";
+		ports = <&ipu_di0>, <&ipu_di1>;
+	};

The ports are the two display output port nodes of the image processing
unit (corresponding to a drm_crtc each), and the imx-drm driver that
binds to the compatible value "fsl,imx-display-subsystem" automatically
collects all encoders that hang off of those via the OF graph bindings
(as documented in Documentation/devicetree/bindings/graph.txt in the
staging tree). I don't know how well those bindings would fit on Exynos,
maybe you could consider aligning your bindings with those.

Either way, the generic term 'display-subsystem' is preferable to 'drm',
as the latter is Linux specific, which the device tree bindings
shouldn't be. The same goes for the 'crtcs' property. I'd prefer to
avoid Linux specific legacy names in new device tree bindings.

Also, since this adds new bindings, it should probably be sent to the
devicetree mailing list and include some documentation.

If you are interested in the previous discussion on the imx-drm
supernode, here is the thread history:
    "[PATCH v5 00/11] imx-drm dt bindings"
    http://www.spinics.net/lists/arm-kernel/msg313112.html
    "[PATCH v4 00/11] imx-drm dt bindings"
    http://www.spinics.net/lists/dri-devel/msg54353.html
    "[RFC PATCH v3 0/9] imx-drm dt bindings"
    http://www.spinics.net/lists/arm-kernel/msg308529.html
    "[RFC PATCH v2 0/4] imx-drm dt bindings"
    http://www.spinics.net/lists/arm-kernel/msg306649.html
    "[RFC PATCH 0/3] imx-drm dt bindings"
    http://www.spinics.net/lists/arm-kernel/msg298290.html

regards
Philipp