drm/i915: Add i915_sched_engine destroy vfunc

This is required to allow backend specific cleanup

v2:
 (John H)
  - Rework commit message
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727002348.97202-7-matthew.brost@intel.com

drivers/gpu/drm/i915/i915_scheduler.c

@@ -431,7 +431,7 @@ void i915_request_show_with_schedule(struct drm_printer *m,
 	rcu_read_unlock();
 }
 
-void i915_sched_engine_free(struct kref *kref)
+static void default_destroy(struct kref *kref)
 {
 	struct i915_sched_engine *sched_engine =
 		container_of(kref, typeof(*sched_engine), ref);
@@ -453,6 +453,7 @@ i915_sched_engine_create(unsigned int subclass)
 
 	sched_engine->queue = RB_ROOT_CACHED;
 	sched_engine->queue_priority_hint = INT_MIN;
+	sched_engine->destroy = default_destroy;
 
 	INIT_LIST_HEAD(&sched_engine->requests);
 	INIT_LIST_HEAD(&sched_engine->hold);

drivers/gpu/drm/i915/i915_scheduler.h

@@ -51,8 +51,6 @@ static inline void i915_priolist_free(struct i915_priolist *p)
 struct i915_sched_engine *
 i915_sched_engine_create(unsigned int subclass);
 
-void i915_sched_engine_free(struct kref *kref);
-
 static inline struct i915_sched_engine *
 i915_sched_engine_get(struct i915_sched_engine *sched_engine)
 {
@@ -63,7 +61,7 @@ i915_sched_engine_get(struct i915_sched_engine *sched_engine)
 static inline void
 i915_sched_engine_put(struct i915_sched_engine *sched_engine)
 {
-	kref_put(&sched_engine->ref, i915_sched_engine_free);
+	kref_put(&sched_engine->ref, sched_engine->destroy);
 }
 
 static inline bool

drivers/gpu/drm/i915/i915_scheduler_types.h

@@ -163,6 +163,11 @@ struct i915_sched_engine {
 	 */
 	void *private_data;
 
+	/**
+	 * @destroy: destroy schedule engine / cleanup in backend
+	 */
+	void	(*destroy)(struct kref *kref);
+
 	/**
 	 * @kick_backend: kick backend after a request's priority has changed
 	 */