AIUI, the “Direct Rendering Manager” is responsible for the display change when you press ctrl-alt-Fn#. Once upon a time, Xfree86 or svgalib would directly poke registers in the video card. If a program crashed with the video card in a weird state, you’re pretty much stuck with that until you do a blind reboot. The kernel had very little idea about what was going on with the video card.
Under DRM, the kernel now knows about the video card’s state. The kernel handles resolution or dotclocks or whatever, and hands out mmaps of framebuffers and command buffers to programs. I think. The kernel is supposed to gatekeep any commands that may put the display into a deranged, all-you-can-do-now-is-power-it-down state.
AIUI, the “Direct Rendering Manager” is responsible for the display change when you press ctrl-alt-Fn#. Once upon a time, Xfree86 or svgalib would directly poke registers in the video card. If a program crashed with the video card in a weird state, you’re pretty much stuck with that until you do a blind reboot. The kernel had very little idea about what was going on with the video card.
Under DRM, the kernel now knows about the video card’s state. The kernel handles resolution or dotclocks or whatever, and hands out mmaps of framebuffers and command buffers to programs. I think. The kernel is supposed to gatekeep any commands that may put the display into a deranged, all-you-can-do-now-is-power-it-down state.