drm/bridge: Add a devm_ allocator for panel bridge.

This will let drivers reduce the error cleanup they need, in
particular the "is_panel_bridge" flag.

v2: Slight cleanup of remove function by Andrzej

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Philippe Cornu <philippe.cornu@st.com>
Tested-by: Philippe Cornu <philippe.cornu@st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170718210510.12229-2-eric@anholt.net

drivers/gpu/drm/bridge/panel.c

@@ -195,3 +195,33 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge)
 	devm_kfree(panel_bridge->panel->dev, bridge);
 }
 EXPORT_SYMBOL(drm_panel_bridge_remove);
+
+static void devm_drm_panel_bridge_release(struct device *dev, void *res)
+{
+	struct drm_bridge **bridge = res;
+
+	drm_panel_bridge_remove(*bridge);
+}
+
+struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
+					     struct drm_panel *panel,
+					     u32 connector_type)
+{
+	struct drm_bridge **ptr, *bridge;
+
+	ptr = devres_alloc(devm_drm_panel_bridge_release, sizeof(*ptr),
+			   GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	bridge = drm_panel_bridge_add(panel, connector_type);
+	if (!IS_ERR(bridge)) {
+		*ptr = bridge;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return bridge;
+}
+EXPORT_SYMBOL(devm_drm_panel_bridge_add);

include/drm/drm_bridge.h

@@ -268,6 +268,9 @@ void drm_bridge_enable(struct drm_bridge *bridge);
 struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel,
 					u32 connector_type);
 void drm_panel_bridge_remove(struct drm_bridge *bridge);
+struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
+					     struct drm_panel *panel,
+					     u32 connector_type);
 #endif
 
 #endif