On Mon, May 16, 2016 at 7:47 AM, Maxime Ripard maxime.ripard@free-electrons.com wrote:
Some boards have an entirely passive RGB to VGA bridge, based on either DACs or resistor ladders.
Those might or might not have an i2c bus routed to the VGA connector in order to access the screen EDIDs.
Add a bridge that doesn't do anything but expose the modes available on the screen, either based on the EDIDs if available, or based on the XGA standards.
Signed-off-by: Maxime Ripard maxime.ripard@free-electrons.com
.../bindings/display/bridge/dumb-vga.txt | 40 +++++ drivers/gpu/drm/bridge/Kconfig | 6 + drivers/gpu/drm/bridge/Makefile | 1 + drivers/gpu/drm/bridge/dumb-vga.c | 186 +++++++++++++++++++++ 4 files changed, 233 insertions(+) create mode 100644 Documentation/devicetree/bindings/display/bridge/dumb-vga.txt create mode 100644 drivers/gpu/drm/bridge/dumb-vga.c
diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt new file mode 100644 index 000000000000..757f04de97f3 --- /dev/null +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt @@ -0,0 +1,40 @@ +Passive RGB to VGA bridge +-------------------------
+This binding is aimed for entirely passive RGB to VGA bridges that do not +require any configuration.
No reset or enable lines or regulators?
+Required properties:
+- compatible: Should be "dumb-vga-bridge"
+Optional properties:
+- ddc-i2c-bus: phandle to the i2c bus used to communicate with the monitor
The i2c bus is a property of the connector, not the bridge chip, so it belongs in a VGA connector node (which we already have binding for).
I think for the really "dumb" (or transparent case), you should only have a connector. For anything more complex, then you should have both a DAC and connector node.
On the driver side, I think we could handle multiple connectors with a single driver. Ideally, that would work with any DRM driver that has a connector node.
+Required nodes:
+This device has one video port. Its connection is modelled using the OF +graph bindings specified in Documentation/devicetree/bindings/graph.txt. This +connection is meant to be the RGB input bus.
+Example +-------
+bridge {
compatible = "dumb-vga-bridge";#address-cells = <1>;#size-cells = <0>;port@0 {reg = <0>;#address-cells = <1>;#size-cells = <0>;vga_input: endpoint@0 {reg = <0>;remote-endpoint = <&tcon0_out_vga>;};};+};