New DRI3 v1.1 & v1.2 Bits Now Supported By Mesa
Landing in Mesa 18.1-devel Git yesterday was DRI3 v1.2 support within the Vulkan WSI (Windowing System Integration) code used by both RADV and ANV for supporting multiple planes and buffer modifiers.
Within the EGL/X11 update was also support for DRI3 v1.1 for allowing pixmaps to be backed by multi-planar buffers.
Those patches and the related code by Collabora amount to a few hundred lines of new code in Mesa. Obviously you need to be making use of X.Org Server 1.20+ and the other necessary X updates for supporting the updated DRI3 support. X.Org Server 1.20 should be released as stable within the next few weeks. Mesa 18.1 will be released around late May or June.