drm/bridge: Make the bridge chain a double-linked list

So that each element in the chain can easily access its predecessor.
This will be needed to support bus format negotiation between elements
of the bridge chain.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203141515.3597631-5-boris.brezillon@collabora.com

drivers/gpu/drm/drm_bridge.c

@@ -55,7 +55,7 @@
  * just provide additional hooks to get the desired output at the end of the
  * encoder chain.
  *
- * Bridges can also be chained up using the &drm_bridge.next pointer.
+ * Bridges can also be chained up using the &drm_bridge.chain_node field.
  *
  * Both legacy CRTC helpers and the new atomic modeset helpers support bridges.
  */
@@ -128,20 +128,21 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 	bridge->dev = encoder->dev;
 	bridge->encoder = encoder;
 
+	if (previous)
+		list_add(&bridge->chain_node, &previous->chain_node);
+	else
+		list_add(&bridge->chain_node, &encoder->bridge_chain);
+
 	if (bridge->funcs->attach) {
 		ret = bridge->funcs->attach(bridge);
 		if (ret < 0) {
+			list_del(&bridge->chain_node);
 			bridge->dev = NULL;
 			bridge->encoder = NULL;
 			return ret;
 		}
 	}
 
-	if (previous)
-		previous->next = bridge;
-	else
-		encoder->bridge = bridge;
-
 	return 0;
 }
 EXPORT_SYMBOL(drm_bridge_attach);
@@ -157,6 +158,7 @@ void drm_bridge_detach(struct drm_bridge *bridge)
 	if (bridge->funcs->detach)
 		bridge->funcs->detach(bridge);
 
+	list_del(&bridge->chain_node);
 	bridge->dev = NULL;
 }
 
@@ -190,18 +192,21 @@ bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
 				 const struct drm_display_mode *mode,
 				 struct drm_display_mode *adjusted_mode)
 {
-	bool ret = true;
+	struct drm_encoder *encoder;
 
 	if (!bridge)
 		return true;
 
-	if (bridge->funcs->mode_fixup)
-		ret = bridge->funcs->mode_fixup(bridge, mode, adjusted_mode);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (!bridge->funcs->mode_fixup)
+			continue;
 
-	ret = ret && drm_bridge_chain_mode_fixup(bridge->next, mode,
-						 adjusted_mode);
+		if (!bridge->funcs->mode_fixup(bridge, mode, adjusted_mode))
+			return false;
+	}
 
-	return ret;
+	return true;
 }
 EXPORT_SYMBOL(drm_bridge_chain_mode_fixup);
 
@@ -224,18 +229,24 @@ enum drm_mode_status
 drm_bridge_chain_mode_valid(struct drm_bridge *bridge,
 			    const struct drm_display_mode *mode)
 {
-	enum drm_mode_status ret = MODE_OK;
+	struct drm_encoder *encoder;
 
 	if (!bridge)
-		return ret;
+		return MODE_OK;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		enum drm_mode_status ret;
+
+		if (!bridge->funcs->mode_valid)
+			continue;
 
-	if (bridge->funcs->mode_valid)
 		ret = bridge->funcs->mode_valid(bridge, mode);
+		if (ret != MODE_OK)
+			return ret;
+	}
 
-	if (ret != MODE_OK)
-		return ret;
-
-	return drm_bridge_chain_mode_valid(bridge->next, mode);
+	return MODE_OK;
 }
 EXPORT_SYMBOL(drm_bridge_chain_mode_valid);
 
@@ -251,13 +262,20 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_valid);
  */
 void drm_bridge_chain_disable(struct drm_bridge *bridge)
 {
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
 	if (!bridge)
 		return;
 
-	drm_bridge_chain_disable(bridge->next);
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->disable)
+			iter->funcs->disable(iter);
 
-	if (bridge->funcs->disable)
-		bridge->funcs->disable(bridge);
+		if (iter == bridge)
+			break;
+	}
 }
 EXPORT_SYMBOL(drm_bridge_chain_disable);
 
@@ -274,13 +292,16 @@ EXPORT_SYMBOL(drm_bridge_chain_disable);
  */
 void drm_bridge_chain_post_disable(struct drm_bridge *bridge)
 {
+	struct drm_encoder *encoder;
+
 	if (!bridge)
 		return;
 
-	if (bridge->funcs->post_disable)
-		bridge->funcs->post_disable(bridge);
-
-	drm_bridge_chain_post_disable(bridge->next);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->post_disable)
+			bridge->funcs->post_disable(bridge);
+	}
 }
 EXPORT_SYMBOL(drm_bridge_chain_post_disable);
 
@@ -300,13 +321,16 @@ void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
 			       const struct drm_display_mode *mode,
 			       const struct drm_display_mode *adjusted_mode)
 {
+	struct drm_encoder *encoder;
+
 	if (!bridge)
 		return;
 
-	if (bridge->funcs->mode_set)
-		bridge->funcs->mode_set(bridge, mode, adjusted_mode);
-
-	drm_bridge_chain_mode_set(bridge->next, mode, adjusted_mode);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->mode_set)
+			bridge->funcs->mode_set(bridge, mode, adjusted_mode);
+	}
 }
 EXPORT_SYMBOL(drm_bridge_chain_mode_set);
 
@@ -323,13 +347,17 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_set);
  */
 void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
 {
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
 	if (!bridge)
 		return;
 
-	drm_bridge_chain_pre_enable(bridge->next);
-
-	if (bridge->funcs->pre_enable)
-		bridge->funcs->pre_enable(bridge);
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->pre_enable)
+			iter->funcs->pre_enable(iter);
+	}
 }
 EXPORT_SYMBOL(drm_bridge_chain_pre_enable);
 
@@ -345,13 +373,16 @@ EXPORT_SYMBOL(drm_bridge_chain_pre_enable);
  */
 void drm_bridge_chain_enable(struct drm_bridge *bridge)
 {
+	struct drm_encoder *encoder;
+
 	if (!bridge)
 		return;
 
-	if (bridge->funcs->enable)
-		bridge->funcs->enable(bridge);
-
-	drm_bridge_chain_enable(bridge->next);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->enable)
+			bridge->funcs->enable(bridge);
+	}
 }
 EXPORT_SYMBOL(drm_bridge_chain_enable);
 
@@ -370,15 +401,22 @@ EXPORT_SYMBOL(drm_bridge_chain_enable);
 void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
 				     struct drm_atomic_state *state)
 {
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
 	if (!bridge)
 		return;
 
-	drm_atomic_bridge_chain_disable(bridge->next, state);
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->atomic_disable)
+			iter->funcs->atomic_disable(iter, state);
+		else if (iter->funcs->disable)
+			iter->funcs->disable(iter);
 
-	if (bridge->funcs->atomic_disable)
-		bridge->funcs->atomic_disable(bridge, state);
-	else if (bridge->funcs->disable)
-		bridge->funcs->disable(bridge);
+		if (iter == bridge)
+			break;
+	}
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
 
@@ -398,15 +436,18 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
 void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
 					  struct drm_atomic_state *state)
 {
+	struct drm_encoder *encoder;
+
 	if (!bridge)
 		return;
 
-	if (bridge->funcs->atomic_post_disable)
-		bridge->funcs->atomic_post_disable(bridge, state);
-	else if (bridge->funcs->post_disable)
-		bridge->funcs->post_disable(bridge);
-
-	drm_atomic_bridge_chain_post_disable(bridge->next, state);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->atomic_post_disable)
+			bridge->funcs->atomic_post_disable(bridge, state);
+		else if (bridge->funcs->post_disable)
+			bridge->funcs->post_disable(bridge);
+	}
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
 
@@ -426,15 +467,22 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
 void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
 					struct drm_atomic_state *state)
 {
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
 	if (!bridge)
 		return;
 
-	drm_atomic_bridge_chain_pre_enable(bridge->next, state);
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->atomic_pre_enable)
+			iter->funcs->atomic_pre_enable(iter, state);
+		else if (iter->funcs->pre_enable)
+			iter->funcs->pre_enable(iter);
 
-	if (bridge->funcs->atomic_pre_enable)
-		bridge->funcs->atomic_pre_enable(bridge, state);
-	else if (bridge->funcs->pre_enable)
-		bridge->funcs->pre_enable(bridge);
+		if (iter == bridge)
+			break;
+	}
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
 
@@ -453,15 +501,18 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
 void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 				    struct drm_atomic_state *state)
 {
+	struct drm_encoder *encoder;
+
 	if (!bridge)
 		return;
 
-	if (bridge->funcs->atomic_enable)
-		bridge->funcs->atomic_enable(bridge, state);
-	else if (bridge->funcs->enable)
-		bridge->funcs->enable(bridge);
-
-	drm_atomic_bridge_chain_enable(bridge->next, state);
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->atomic_enable)
+			bridge->funcs->atomic_enable(bridge, state);
+		else if (bridge->funcs->enable)
+			bridge->funcs->enable(bridge);
+	}
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);