DRM Synchronization Object Improvements Queued For Linux 4.14

Introduced in the Linux 4.13 kernel for the Direct Rendering Manager drivers was the concept of DRM synchronization objects while for Linux 4.14 this feature will be improved upon.

DRM synchronization objects (also referred to as "syncobj") are a top-level DRM object that contains a pointer to a fence, with that fence in turn updated via the command submission ioctls. Synchronization objects can be passed between objects. This work was added for supporting Vulkan external semaphores among other possible use-cases.

Now queued in DRM-Next for in turn landing with Linux 4.14 are more improvements to the DRM synchronization object code.

Landing tonight is a wait interface for allowing sync objects to be used to back Vulkan fences, with this code being based upon the AMDGPU code.

There is also now a signal ioctl, so user-space can trigger a sync object directly. This IOCTL is motivated too by Vulkan fences. Also related is a reset ioctl for this syncobj code, among some other improvements now in DRM-Next Git.