Vertical sync and KMS

[Sylvain Beucler <beuc@beuc.net>]

Hi,

Since the switch to KMS (Kernel Mode Setting) in the current Debian, I
cannot get vertical sync to work with free 3D drivers.

(Vertical syncs caps the game framerate to the physical screen's
refresh rate, typically 60Hz, avoiding tearing and unnecessary display
updates, and permitting smooth scrolling.)

The only way to get vsync back is either use a proprietary driver or
switch back to UMS (in either case: when that's actually possible).  I
tried with 2 ATI Radeon cards and an Intel one, using a simple
scrolling demo with bare OpenGL, SDL 1.3 and Pyglet.

Do you get this issue in other distros, and do you know what's the
cause?

Cheers!

-- 
Sylvain