All you need to know about configuring kernel modesetting is written here:
Any one know what does the following option does, the 4870 works well in debian testing with the open src driver. 3d was only openGL 1.5 but 2d was lightning fast so I did not try this option. Kernel is custom one built by myself.
Enable modesetting on radeon by default - NEW DRIVER
I have not been able to find much info on this setting on net and currently do not have the spare time availible to go through the src. Past experience shows that will take ages to decipher the driver.
If you enable that option, you will get OpenGL 2.1, and a native-resolution framebuffer by default. The 3d performance might be slightly lower.
Pretty much all the new development today is focused on the kernel modesetting codepath anyway.
That's even better.
I haven't tested the UMS codepath for a long time now.
Another thing you get with KMS is DRI2.
Thanks for the replies, silly me I had a previous version of the radeonBuildHowto and i did not know that it had been updated. I have never had that much trouble with FGLRX but the OS driver is great, simply just works.