Enable legacy drivers (DANGEROUS)

configname: CONFIG_DRM_LEGACY

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
└─>Enable legacy drivers (DANGEROUS)
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Enable legacy DRI1 drivers. Those drivers expose unsafe and dangerous
APIs to user-space, which can be used to circumvent access
restrictions and other security measures. For backwards compatibility
those drivers are still available, but their use is highly
inadvisable and might harm your system.

You are recommended to use the safe modeset-only drivers instead, and
perform 3D emulation in user-space.

Unless you have strong reasons to go rogue, say "N".