[RFC][PATCH 1/3] drm: drm_syncobj: Add note in DOC about absolute timeout values

[John Stultz]

After having to debug down through the kernel to figure out
why my _WAIT calls were always timing out, I realized its
an absolute timeout value instead of the more common relative
timeouts.

This detail should be called out in the documentation, as while
the absolute value makes sense here, its not as common for timeout
values.

Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Jason Ekstrand <jason at jlekstrand.net>
Cc: Christian König <christian.koenig at amd.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Cc: Chunming Zhou <david1.zhou at amd.com>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: John Stultz <jstultz at google.com>
---
 drivers/gpu/drm/drm_syncobj.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 7e48dcd1bee4..b84d842a1c21 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -136,6 +136,10 @@
  * requirement is inherited from the wait-before-signal behavior required by
  * the Vulkan timeline semaphore API.
  *
+ * It should be noted, that both &DRM_IOCTL_SYNCOBJ_WAIT and
+ * &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT takes an *absolute* CLOCK_MONOTONIC
+ * nanosecond value for the timeout value. Accidentally passing relative time
+ * values will likely result in an immediate -ETIME return.
  *
  * Import/export of syncobjs
  * -------------------------
-- 
2.37.0.144.g8ac04bfd2-goog