1config DRM_RADEON_KMS 2 bool "Enable modesetting on radeon by default - NEW DRIVER" 3 depends on DRM_RADEON 4 select BACKLIGHT_CLASS_DEVICE 5 help 6 Choose this option if you want kernel modesetting enabled by default. 7 8 This is a completely new driver. It's only part of the existing drm 9 for compatibility reasons. It requires an entirely different graphics 10 stack above it and works very differently from the old drm stack. 11 i.e. don't enable this unless you know what you are doing it may 12 cause issues or bugs compared to the previous userspace driver stack. 13 14 When kernel modesetting is enabled the IOCTL of radeon/drm 15 driver are considered as invalid and an error message is printed 16 in the log and they return failure. 17 18 KMS enabled userspace will use new API to talk with the radeon/drm 19 driver. The new API provide functions to create/destroy/share/mmap 20 buffer object which are then managed by the kernel memory manager 21 (here TTM). In order to submit command to the GPU the userspace 22 provide a buffer holding the command stream, along this buffer 23 userspace have to provide a list of buffer object used by the 24 command stream. The kernel radeon driver will then place buffer 25 in GPU accessible memory and will update command stream to reflect 26 the position of the different buffers. 27 28 The kernel will also perform security check on command stream 29 provided by the user, we want to catch and forbid any illegal use 30 of the GPU such as DMA into random system memory or into memory 31 not owned by the process supplying the command stream. 32