drm/atomic: Add atomic_print_state to private objects

A number of drivers (amdgpu, komeda, vc4, etc.) leverage the
drm_private_state structure, but we don't have any infrastructure to
provide debugging like we do for the other components state. Let's add
an atomic_print_state hook to be consistent.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220328124304.2309418-3-maxime@cerno.tech

drivers/gpu/drm/drm_atomic.c

@@ -789,6 +789,8 @@ drm_atomic_private_obj_init(struct drm_device *dev,
 	obj->state = state;
 	obj->funcs = funcs;
 	list_add_tail(&obj->head, &dev->mode_config.privobj_list);
+
+	state->obj = obj;
 }
 EXPORT_SYMBOL(drm_atomic_private_obj_init);
 
@@ -1636,6 +1638,15 @@ int __drm_atomic_helper_set_config(struct drm_mode_set *set,
 }
 EXPORT_SYMBOL(__drm_atomic_helper_set_config);
 
+static void drm_atomic_private_obj_print_state(struct drm_printer *p,
+					       const struct drm_private_state *state)
+{
+	struct drm_private_obj *obj = state->obj;
+
+	if (obj->funcs->atomic_print_state)
+		obj->funcs->atomic_print_state(p, state);
+}
+
 /**
  * drm_atomic_print_new_state - prints drm atomic state
  * @state: atomic configuration to check
@@ -1656,6 +1667,8 @@ void drm_atomic_print_new_state(const struct drm_atomic_state *state,
 	struct drm_crtc_state *crtc_state;
 	struct drm_connector *connector;
 	struct drm_connector_state *connector_state;
+	struct drm_private_obj *obj;
+	struct drm_private_state *obj_state;
 	int i;
 
 	if (!p) {
@@ -1673,6 +1686,9 @@ void drm_atomic_print_new_state(const struct drm_atomic_state *state,
 
 	for_each_new_connector_in_state(state, connector, connector_state, i)
 		drm_atomic_connector_print_state(p, connector_state);
+
+	for_each_new_private_obj_in_state(state, obj, obj_state, i)
+		drm_atomic_private_obj_print_state(p, obj_state);
 }
 EXPORT_SYMBOL(drm_atomic_print_new_state);
 

include/drm/drm_atomic.h

@@ -227,6 +227,18 @@ struct drm_private_state_funcs {
 	 */
 	void (*atomic_destroy_state)(struct drm_private_obj *obj,
 				     struct drm_private_state *state);
+
+	/**
+	 * @atomic_print_state:
+	 *
+	 * If driver subclasses &struct drm_private_state, it should implement
+	 * this optional hook for printing additional driver specific state.
+	 *
+	 * Do not call this directly, use drm_atomic_private_obj_print_state()
+	 * instead.
+	 */
+	void (*atomic_print_state)(struct drm_printer *p,
+				   const struct drm_private_state *state);
 };
 
 /**
@@ -311,14 +323,21 @@ struct drm_private_obj {
 
 /**
  * struct drm_private_state - base struct for driver private object state
- * @state: backpointer to global drm_atomic_state
  *
- * Currently only contains a backpointer to the overall atomic update, but in
- * the future also might hold synchronization information similar to e.g.
- * &drm_crtc.commit.
+ * Currently only contains a backpointer to the overall atomic update,
+ * and the relevant private object but in the future also might hold
+ * synchronization information similar to e.g. &drm_crtc.commit.
  */
 struct drm_private_state {
+	/**
+	 * @state: backpointer to global drm_atomic_state
+	 */
 	struct drm_atomic_state *state;
+
+	/**
+	 * @obj: backpointer to the private object
+	 */
+	struct drm_private_obj *obj;
 };
 
 struct __drm_private_objs_state {