[RFC 3/3] drm/sched: Disallow initializing entities with no schedulers

[Tvrtko Ursulin <tvrtko.ursulin@igalia.com>]

Since we have removed the case where amdgpu was initializing entitites
with either no schedulers on the list, or with a single NULL scheduler,
and there appears no other drivers which rely on this, we can simplify the
scheduler by explictly rejecting that early.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
---
 drivers/gpu/drm/scheduler/sched_entity.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index fe174a4857be..bb7e5fc47f99 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -61,32 +61,27 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
 			  unsigned int num_sched_list,
 			  atomic_t *guilty)
 {
-	if (!(entity && sched_list && (num_sched_list == 0 || sched_list[0])))
+	if (!entity || !sched_list || !num_sched_list || !sched_list[0])
 		return -EINVAL;
 
 	memset(entity, 0, sizeof(struct drm_sched_entity));
 	INIT_LIST_HEAD(&entity->list);
 	entity->rq = NULL;
 	entity->guilty = guilty;
-	entity->num_sched_list = num_sched_list;
 	entity->priority = priority;
 	entity->last_user = current->group_leader;
-	/*
-	 * It's perfectly valid to initialize an entity without having a valid
-	 * scheduler attached. It's just not valid to use the scheduler before it
-	 * is initialized itself.
-	 */
+	entity->num_sched_list = num_sched_list;
 	entity->sched_list = num_sched_list > 1 ? sched_list : NULL;
 	RCU_INIT_POINTER(entity->last_scheduled, NULL);
 	RB_CLEAR_NODE(&entity->rb_tree_node);
 
-	if (num_sched_list && !sched_list[0]->sched_rq) {
+	if (!sched_list[0]->sched_rq) {
 		/* Since every entry covered by num_sched_list
 		 * should be non-NULL and therefore we warn drivers
 		 * not to do this and to fix their DRM calling order.
 		 */
 		pr_warn("%s: called with uninitialized scheduler\n", __func__);
-	} else if (num_sched_list) {
+	} else {
 		/* The "priority" of an entity cannot exceed the number of run-queues of a
 		 * scheduler. Protect against num_rqs being 0, by converting to signed. Choose
 		 * the lowest priority available.
-- 
2.52.0