Valve has funded work by LunarG on a project codenamed "Glassy Mesa" to deliver potential performance improvements on the open-source Mesa graphics driver stack.
Glassy Mesa is an experimental project using LunarGLASS for plugging LLVM into Mesa for shader compilation and run-time improvements. LunarGLASS originated back in 2010 as using LLVM IR as the base intermediate representation for the shader and kernel compiler stack. LunarGLASS has performance potential via taking advantage of LLVM's many optimization passes.
I’ve added to the Steam package repository for Fedora an alternative kernel module for xpad, the X-Box gamepad driver. This variant contains patches created by Valve to improve the driver and its behaviour.
The module is available in both akmod (RPMFusion) and dkms package formats.
This made my 3rd party X-Box controller work without any issue in Steam games and in the Big Picture Mode interface!