Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)

modulename: drm.ko

configname: CONFIG_DRM

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>/dev/agpgart (AGP Support)
└─>/dev/agpgart (AGP Support)
└─>Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)
In linux kernel since version 2.6.12  
Kernel-level support for the Direct Rendering Infrastructure (DRI)
introduced in XFree86 4.0. If you say Y here, you need to select
the module that's right for your graphics card from the list below.
These modules provide support for synchronization, security, and
DMA transfers. Please see <http://dri.sourceforge.net/> for more
details. You should also select and configure AGP
(/dev/agpgart) support if it is available for your platform.

source code:
drivers/gpu/drm//