drm/bridge: Clarify the atomic enable/disable hooks semantics

The [pre_]enable/[post_]disable hooks are passed the old atomic state.
Update the doc and rename the arguments to make it clear.
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203141515.3597631-8-boris.brezillon@collabora.com

drivers/gpu/drm/drm_bridge.c

@@ -389,7 +389,7 @@ EXPORT_SYMBOL(drm_bridge_chain_enable);
 /**
  * drm_atomic_bridge_chain_disable - disables all bridges in the encoder chain
  * @bridge: bridge control structure
- * @state: atomic state being committed
+ * @old_state: old atomic state
  *
  * Calls &drm_bridge_funcs.atomic_disable (falls back on
  * &drm_bridge_funcs.disable) op for all the bridges in the encoder chain,
@@ -399,7 +399,7 @@ EXPORT_SYMBOL(drm_bridge_chain_enable);
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
-				     struct drm_atomic_state *state)
+				     struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
 	struct drm_bridge *iter;
@@ -410,7 +410,7 @@ void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
 	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);
+			iter->funcs->atomic_disable(iter, old_state);
 		else if (iter->funcs->disable)
 			iter->funcs->disable(iter);
 
@@ -424,7 +424,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
  * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
  *					  in the encoder chain
  * @bridge: bridge control structure
- * @state: atomic state being committed
+ * @old_state: old atomic state
  *
  * Calls &drm_bridge_funcs.atomic_post_disable (falls back on
  * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
@@ -434,7 +434,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
-					  struct drm_atomic_state *state)
+					  struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
 
@@ -444,7 +444,7 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
 	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);
+			bridge->funcs->atomic_post_disable(bridge, old_state);
 		else if (bridge->funcs->post_disable)
 			bridge->funcs->post_disable(bridge);
 	}
@@ -455,7 +455,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
  * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
  *					the encoder chain
  * @bridge: bridge control structure
- * @state: atomic state being committed
+ * @old_state: old atomic state
  *
  * Calls &drm_bridge_funcs.atomic_pre_enable (falls back on
  * &drm_bridge_funcs.pre_enable) op for all the bridges in the encoder chain,
@@ -465,7 +465,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
-					struct drm_atomic_state *state)
+					struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
 	struct drm_bridge *iter;
@@ -476,7 +476,7 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
 	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);
+			iter->funcs->atomic_pre_enable(iter, old_state);
 		else if (iter->funcs->pre_enable)
 			iter->funcs->pre_enable(iter);
 
@@ -489,7 +489,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
 /**
  * drm_atomic_bridge_chain_enable - enables all bridges in the encoder chain
  * @bridge: bridge control structure
- * @state: atomic state being committed
+ * @old_state: old atomic state
  *
  * Calls &drm_bridge_funcs.atomic_enable (falls back on
  * &drm_bridge_funcs.enable) op for all the bridges in the encoder chain,
@@ -499,7 +499,7 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
  * Note: the bridge passed should be the one closest to the encoder
  */
 void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
-				    struct drm_atomic_state *state)
+				    struct drm_atomic_state *old_state)
 {
 	struct drm_encoder *encoder;
 
@@ -509,7 +509,7 @@ void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 	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);
+			bridge->funcs->atomic_enable(bridge, old_state);
 		else if (bridge->funcs->enable)
 			bridge->funcs->enable(bridge);
 	}

include/drm/drm_bridge.h

@@ -263,7 +263,7 @@ struct drm_bridge_funcs {
 	 * The @atomic_pre_enable callback is optional.
 	 */
 	void (*atomic_pre_enable)(struct drm_bridge *bridge,
-				  struct drm_atomic_state *state);
+				  struct drm_atomic_state *old_state);
 
 	/**
 	 * @atomic_enable:
@@ -288,7 +288,7 @@ struct drm_bridge_funcs {
 	 * The @atomic_enable callback is optional.
 	 */
 	void (*atomic_enable)(struct drm_bridge *bridge,
-			      struct drm_atomic_state *state);
+			      struct drm_atomic_state *old_state);
 	/**
 	 * @atomic_disable:
 	 *
@@ -311,7 +311,7 @@ struct drm_bridge_funcs {
 	 * The @atomic_disable callback is optional.
 	 */
 	void (*atomic_disable)(struct drm_bridge *bridge,
-			       struct drm_atomic_state *state);
+			       struct drm_atomic_state *old_state);
 
 	/**
 	 * @atomic_post_disable:
@@ -337,7 +337,7 @@ struct drm_bridge_funcs {
 	 * The @atomic_post_disable callback is optional.
 	 */
 	void (*atomic_post_disable)(struct drm_bridge *bridge,
-				    struct drm_atomic_state *state);
+				    struct drm_atomic_state *old_state);
 };
 
 /**