I'm testing KMS and DRI2 (from git builds) with my old ATI 9600 Mobility (R300) card. I also use external VGA and the problem is that radeon framebuffer driver cannot properly recognize my connected VGA monitor. It uses wrong frequencies (monitor says out of range). Furthermore, laptop's builtin LCD uses only 800x600 instead of 1024x768 (which is properly recognized without connected VGA monitor or without KMS). I reported this bug, you can find it here: https://bugs.freedesktop.org/show_bug.cgi?id=25010
The problem is not only that fbcon uses wrong display resolution but there are also other issues with Xorg. I can tell XRandr (xorg.conf modeline and frequencies are ignored) to add and use new mode - 1280x1024 for VGA-0 but lot of other things get crippled because of this change.
I would like to ask if there are some kernel/module arguments which could tell the driver to use specific frequencies given by the cmdline and also which monitor to use.