Nouveau X.Org Driver To Drop Maxwell & GLAMOR Support
Prolific Nouveau contributor Ilia Mirkin published the patches a few days ago on the Nouveau mailing list to remove GLAMOR and Maxwell support. GLAMOR -- the means of doing 2D over OpenGL with the generic code built into the xorg-server -- would be dropped in favor of the other NVIDIA hardware on Nouveau that has dedicated 2D code-paths written over EXA acceleration.
As far as why dropping GLAMOR when it's supported by the Intel and Radeon drivers was just this comment in the patch, "If you want glamor, just use modesetting instead." The xf86-video-modesetting driver is generic to any hardware having a DRM/KMS driver and with OpenGL/GLES support is able to provide GLAMOR 2D acceleration.
With dropping GLAMOR, in the next patch Mirkin then goes for dropping the latest-generation Maxwell support from xf86-video-nouveau. As the Nouveau driver doesn't support EXA for Maxwell but relied on GLAMOR, there goes that hardware support that instead can be used xf86-video-modesetting driver.