drm/bridge: Fix lvds-encoder since the panel_bridge rework.

The panel_bridge bridge attaches to the panel's OF node, not the
lvds-encoder's node.  Put in a little no-op bridge of our own so that
our consumers can still find a bridge where they expect.

This also fixes an unintended unregistration and leak of the
panel-bridge on module remove.

Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: 13dfc0540a57 ("drm/bridge: Refactor out the panel wrapper from the lvds-encoder bri
dge.")
Tested-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114191647.22207-1-eric@anholt.net

drivers/gpu/drm/bridge/lvds-encoder.c

@@ -13,13 +13,37 @@
 
 #include <linux/of_graph.h>
 
+struct lvds_encoder {
+	struct drm_bridge bridge;
+	struct drm_bridge *panel_bridge;
+};
+
+static int lvds_encoder_attach(struct drm_bridge *bridge)
+{
+	struct lvds_encoder *lvds_encoder = container_of(bridge,
+							 struct lvds_encoder,
+							 bridge);
+
+	return drm_bridge_attach(bridge->encoder, lvds_encoder->panel_bridge,
+				 bridge);
+}
+
+static struct drm_bridge_funcs funcs = {
+	.attach = lvds_encoder_attach,
+};
+
 static int lvds_encoder_probe(struct platform_device *pdev)
 {
 	struct device_node *port;
 	struct device_node *endpoint;
 	struct device_node *panel_node;
 	struct drm_panel *panel;
-	struct drm_bridge *bridge;
+	struct lvds_encoder *lvds_encoder;
+
+	lvds_encoder = devm_kzalloc(&pdev->dev, sizeof(*lvds_encoder),
+				    GFP_KERNEL);
+	if (!lvds_encoder)
+		return -ENOMEM;
 
 	/* Locate the panel DT node. */
 	port = of_graph_get_port_by_id(pdev->dev.of_node, 1);
@@ -49,20 +73,30 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 		return -EPROBE_DEFER;
 	}
 
-	bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_LVDS);
-	if (IS_ERR(bridge))
-		return PTR_ERR(bridge);
+	lvds_encoder->panel_bridge =
+		devm_drm_panel_bridge_add(&pdev->dev,
+					  panel, DRM_MODE_CONNECTOR_LVDS);
+	if (IS_ERR(lvds_encoder->panel_bridge))
+		return PTR_ERR(lvds_encoder->panel_bridge);
+
+	/* 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.
+	 */
+	lvds_encoder->bridge.of_node = pdev->dev.of_node;
+	lvds_encoder->bridge.funcs = &funcs;
+	drm_bridge_add(&lvds_encoder->bridge);
 
-	platform_set_drvdata(pdev, bridge);
+	platform_set_drvdata(pdev, lvds_encoder);
 
 	return 0;
 }
 
 static int lvds_encoder_remove(struct platform_device *pdev)
 {
-	struct drm_bridge *bridge = platform_get_drvdata(pdev);
+	struct lvds_encoder *lvds_encoder = platform_get_drvdata(pdev);
 
-	drm_bridge_remove(bridge);
+	drm_bridge_remove(&lvds_encoder->bridge);
 
 	return 0;
 }