[PATCH] drm: Detect no-op drmModeAtomicRequest and return early

* [PATCH] drm: Detect no-op drmModeAtomicRequest and return early
@ 2015-07-21 12:50 Chris Wilson
  2015-07-28 13:42 ` Emil Velikov
  0 siblings, 1 reply; 3+ messages in thread
From: Chris Wilson @ 2015-07-21 12:50 UTC (permalink / raw)
  To: dri-devel; +Cc: Daniel Stone, Emil Velikov, Rob Clark

If the number of items to process in the request is zero, we can forgo
duplicating, sorting the request and feeding it into the kernel and
instead report success immediately.  This prevents a NULL dereference of
the sorted->items for the no-op request.

Fixes: ed44e0b9585c563905447eceed12af9c1c7ca8d4
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rob Clark <robclark@freedesktop.org>
Cc: Daniel Stone <daniels@collabora.com>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
---
 xf86drmMode.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xf86drmMode.c b/xf86drmMode.c
index 529429e..fa21986 100644
--- a/xf86drmMode.c
+++ b/xf86drmMode.c
@@ -1289,7 +1289,7 @@ static int sort_req_list(const void *misc, const void *other)
 int drmModeAtomicCommit(int fd, drmModeAtomicReqPtr req, uint32_t flags,
 			void *user_data)
 {
-	drmModeAtomicReqPtr sorted = drmModeAtomicDuplicate(req);
+	drmModeAtomicReqPtr sorted;
 	struct drm_mode_atomic atomic;
 	uint32_t *objs_ptr = NULL;
 	uint32_t *count_props_ptr = NULL;
@@ -1300,7 +1300,11 @@ int drmModeAtomicCommit(int fd, drmModeAtomicReqPtr req, uint32_t flags,
 	int obj_idx = -1;
 	int ret = -1;
 
-	if (!sorted)
+	if (req->cursor == 0)
+		return 0;
+
+	sorted = drmModeAtomicDuplicate(req);
+	if (sorted == NULL)
 		return -ENOMEM;
 
 	memclear(atomic);
-- 
2.1.4

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