The user pointer "userptr" support allows turning a memory pointer supplied by user-space into a buffer object for the DRM kernel graphics driver. Userptr can be used for GPGPU/compute scenarions and other situation for feeding memory objects from user-space to the kernel driver.
Intel's DRM graphics driver in the kernel already led the userptr way and Radeon followed but it wasn't quite ready for Linux 3.17 due to waiting on the Radeon user-space code.
Alex Deucher sent in on Wednesday his initial Radeon DRM pull request for drm-next, which is code that won't land until the Linux 3.18 kernel merge window opens after the Linux 3.17 release. With this first pull request (and more expected in the weeks ahead), the only change over the Radeon Linux 3.17 code is the userptr support.
Separately, Intel has also been lining up its changes for Linux 3.18. The Radeon userptr pull request for drm-next-3.18 can be found on dri-devel.