Semaphores Support Updated For RadeonSI Gallium3D

Andres Rodriguez, one of Valve's Linux GPU driver developers, has sent out his latest 22 patches for enabling semaphores support (GL_EXT_semaphore) within the RadeonSI driver.

At the start of November is when Andres originally posted these patches with this semaphores extension used by SteamVR. The EXT_semaphore support is part of the OpenGL memory object support for adding semaphores / memory object concepts from Vulkan back in OpenGL. Valve makes use of the semaphore extension with SteamVR for synchronizing access to shared surfaces between OpenGL and Vulkan.

This second version of these patches address feedback from other developers that came up for review. Hopefully now it won't be too much longer before hitting Mesa Git master.

These latest RadeonSI semaphores patches for those interested can be found on Mesa-dev.