drm/i915: Update alloc_request to return the allocated request

The alloc_request() function does not actually return the newly allocated
request. Instead, it must be pulled from ring->outstanding_lazy_request. This
patch fixes this so that code can create a request and start using it knowing
exactly which request it actually owns.

v2: Updated for new i915_gem_request_alloc() scheme.

For: VIZ-5115
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Tomas Elf <tomas.elf@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 80705de..a0f5147 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2634,13 +2634,17 @@
 }
 
 int i915_gem_request_alloc(struct intel_engine_cs *ring,
-			   struct intel_context *ctx)
+			   struct intel_context *ctx,
+			   struct drm_i915_gem_request **req_out)
 {
 	struct drm_i915_private *dev_priv = to_i915(ring->dev);
 	struct drm_i915_gem_request *req;
 	int ret;
 
-	if (ring->outstanding_lazy_request)
+	if (!req_out)
+		return -EINVAL;
+
+	if ((*req_out = ring->outstanding_lazy_request) != NULL)
 		return 0;
 
 	req = kmem_cache_zalloc(dev_priv->requests, GFP_KERNEL);
@@ -2686,7 +2690,7 @@
 	 */
 	intel_ring_reserved_space_reserve(req->ringbuf, MIN_SPACE_FOR_ADD_REQUEST);
 
-	ring->outstanding_lazy_request = req;
+	*req_out = ring->outstanding_lazy_request = req;
 	return 0;
 
 err: