[RFC PATCH 3/3] drm: bridge: lvds-encoder: on request, override the bus format

[Peter Rosin]

If the bridge changes the bus format, allow this to be described in
the bridge, instead of providing false information about the bus
format of the panel itself.

Signed-off-by: Peter Rosin <p...@axentia.se>
---
 .../bindings/display/bridge/lvds-transmitter.txt       |  8 ++++++++
 drivers/gpu/drm/bridge/lvds-encoder.c                  | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git 
a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt 
b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
index 9d09190d9210..c0fbe74272e7 100644
--- a/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
+++ b/Documentation/devicetree/bindings/display/bridge/lvds-transmitter.txt
@@ -29,6 +29,14 @@ Required properties:
 
              "ti,ds90c185"
 
+Optional properties:
+
+- interface-pix-fmt:
+             Override the bus format of the panel, in case the bridge
+             converts the signals. Recognized formats include:
+
+             "rgb565"
+
 Required nodes:
 
 This device has two video ports. Their connections are modeled using the OF
diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c 
b/drivers/gpu/drm/bridge/lvds-encoder.c
index 75b0d3f6e4de..acff3a5b0562 100644
--- a/drivers/gpu/drm/bridge/lvds-encoder.c
+++ b/drivers/gpu/drm/bridge/lvds-encoder.c
@@ -39,6 +39,9 @@ static int lvds_encoder_probe(struct platform_device *pdev)
        struct device_node *panel_node;
        struct drm_panel *panel;
        struct lvds_encoder *lvds_encoder;
+       u32 bus_format = 0;
+       const char *fmt;
+       int ret;
 
        lvds_encoder = devm_kzalloc(&pdev->dev, sizeof(*lvds_encoder),
                                    GFP_KERNEL);
@@ -79,6 +82,21 @@ static int lvds_encoder_probe(struct platform_device *pdev)
        if (IS_ERR(lvds_encoder->panel_bridge))
                return PTR_ERR(lvds_encoder->panel_bridge);
 
+       ret = of_property_read_string(pdev->dev.of_node,
+                                     "interface-pix-fmt", &fmt);
+       if (!ret) {
+               if (!strcmp(fmt, "rgb565")) {
+                       bus_format = MEDIA_BUS_FMT_RGB565_1X16;
+               } else {
+                       dev_dbg(&pdev->dev,
+                               "requested interface-pix-fmt not recognized\n");
+                       return -EINVAL;
+               }
+       }
+       if (bus_format)
+               drm_panel_bridge_set_bus_format(lvds_encoder->panel_bridge,
+                                               bus_format);
+
        /* The panel_bridge bridge is attached to the panel's of_node,
         * but we need a bridge attached to our of_node for our user
         * to look up.
-- 
2.11.0