While DragonFly's i915 DRM driver started out as woefully outdated compared to the upstream Linux kernel code, the work done by Tigeot and others is quite close to re-basing against the latest mainline code. With patches published recently, the DragonFlyBSD driver would now be comparable to what's in the Linux 4.0 kernel.
With the latest i915 DRM code for DragonFlyBSD, there is now basic Skylake support, PSR support for Valley View and Cherry View, performance improvements for many recent GPU series, re-clocking changes, improved reset support for older Intel IGPs, better sound/graphics synchronization for HDMI audio, and various bug and stability improvements.
There's a ton of changes for Intel DragonFlyBSD users with this update and the DRM driver increases in size by about 15k lines of code. More details via this mailing list post.
Hopefully in 2016 we'll see DragonFlyBSD catch up to mainline or just being a release or so behind stable, which would be quite an accomplishment. Ideally we'll see this same catch-up with the Radeon DRM driver too.