drivers/gpu/drm/radeon/Kconfig

config DRM_RADEON_KMS
	bool "Enable modesetting on radeon by default"
	depends on DRM_RADEON
	help
	  Choose this option if you want kernel modesetting enabled by default,
	  and you have a new enough userspace to support this. Running old
	  userspaces with this enabled will cause pain.

	  When kernel modesetting is enabled the IOCTL of radeon/drm
	  driver are considered as invalid and an error message is printed
	  in the log and they return failure.

	  KMS enabled userspace will use new API to talk with the radeon/drm
	  driver. The new API provide functions to create/destroy/share/mmap
	  buffer object which are then managed by the kernel memory manager
	  (here TTM). In order to submit command to the GPU the userspace
	  provide a buffer holding the command stream, along this buffer
	  userspace have to provide a list of buffer object used by the
	  command stream. The kernel radeon driver will then place buffer
	  in GPU accessible memory and will update command stream to reflect
	  the position of the different buffers.

	  The kernel will also perform security check on command stream
	  provided by the user, we want to catch and forbid any illegal use
	  of the GPU such as DMA into random system memory or into memory
	  not owned by the process supplying the command stream. This part
	  of the code is still incomplete and this why we propose that patch
	  as a staging driver addition, future security might forbid current
	  experimental userspace to run.

	  This code support the following hardware : R1XX,R2XX,R3XX,R4XX,R5XX
	  (radeon up to X1950). Works is underway to provide support for R6XX,
	  R7XX and newer hardware (radeon from HD2XXX to HD4XXX).