diff options
Diffstat (limited to 'include/uapi')
| -rw-r--r-- | include/uapi/drm/i915_drm.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h index 452629de7a57..5501fe83ed92 100644 --- a/include/uapi/drm/i915_drm.h +++ b/include/uapi/drm/i915_drm.h @@ -855,7 +855,16 @@ struct drm_i915_gem_busy { * having flushed any pending activity), and a non-zero return that * the object is still in-flight on the GPU. (The GPU has not yet * signaled completion for all pending requests that reference the - * object.) + * object.) An object is guaranteed to become idle eventually (so + * long as no new GPU commands are executed upon it). Due to the + * asynchronous nature of the hardware, an object reported + * as busy may become idle before the ioctl is completed. + * + * Furthermore, if the object is busy, which engine is busy is only + * provided as a guide. There are race conditions which prevent the + * report of which engines are busy from being always accurate. + * However, the converse is not true. If the object is idle, the + * result of the ioctl, that all engines are idle, is accurate. * * The returned dword is split into two fields to indicate both * the engines on which the object is being read, and the @@ -878,6 +887,11 @@ struct drm_i915_gem_busy { * execution engines, e.g. multiple media engines, which are * mapped to the same identifier in the EXECBUFFER2 ioctl and * so are not separately reported for busyness. + * + * Caveat emptor: + * Only the boolean result of this query is reliable; that is whether + * the object is idle or busy. The report of which engines are busy + * should be only used as a heuristic. */ __u32 busy; }; |