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Use this property to pass a file descriptor pointer to DRM. Once the Atomic Commit request call returns OUT_FENCE_PTR will be filled with the file descriptor number of a Sync File. This Sync File contains the CRTC fence that will be signaled when all framebuffers present on the Atomic Commit * request for that given CRTC are scanned out on the screen. The Atomic Commit request fails if a invalid pointer is passed. If the Atomic Commit request fails for any other reason the out fence fd returned will be -1. On a Atomic Commit with the DRM_MODE_ATOMIC_TEST_ONLY flag the out fence will also be set to -1. Note that out-fences don't have a special interface to drivers and are internally represented by a &struct drm_pending_vblank_event in struct &drm_crtc_state, which is also used by the nonblocking atomic commit helpers and for the DRM event handling for existing userspace.