/*
* Copyright 2017 Red Hat
* Parts ported from amdgpu (fence wait code).
* Copyright 2016 Advanced Micro Devices, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
*
*/
/**
* DOC: Overview
*
* DRM synchronisation objects (syncobj, see struct &drm_syncobj) provide a
* container for a synchronization primitive which can be used by userspace
* to explicitly synchronize GPU commands, can be shared between userspace
* processes, and can be shared between different DRM drivers.
* Their primary use-case is to implement Vulkan fences and semaphores.
* The syncobj userspace API provides ioctls for several operations:
*
* - Creation and destruction of syncobjs
* - Import and export of syncobjs to/from a syncobj file descriptor
* - Import and export a syncobj's underlying fence to/from a sync file
* - Reset a syncobj (set its fence to NULL)
* - Signal a syncobj (set a trivially signaled fence)
* - Wait for a syncobj's fence to appear and be signaled
*
* The syncobj userspace API also provides operations to manipulate a syncobj
* in terms of a timeline of struct &dma_fence_chain rather than a single
* struct &dma_fence, through the following ope
