I just upgraded to 10.10 last night and I'm having issues now with dual display from my laptop dock. This was working in the previous release with a manual xrandr command:
xrandr --output LVDS1 --off --output DP1 --mode 1920x1080 && xrandr --output VGA1 --mode 1920x1080 --left-of DP1
When I run this now, the DP1 output doesn't have a mode for 1920x1080. The two displays are a matched pair of dell 22" that are both 1920x1080. The laptop/dock is a Lenovo X201 with the Intel graphics in it. The dock does VGA and DisplayPort out.
When I attempt to manually add the mode
xrandr --addmode DP1 1920x1080
and rerun my command, I lose both displays altogether. I have to then blindly reset to just one of them in order to get display back.
If I avoid the 1920 and just attempt to setup DP1 at the 1280x1024 max it thinks it has, then the second display will come up, but obviously looks horrible since it's non-native resolution.
I've grabbed the updated xorg intel driver from the stable X ppa and am running:
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192 VGA1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm 1920x1080 60.0*+ 1280x1024 75.0 60.0 1152x864 75.0 1024x768 75.1 60.0 800x600 75.0 60.3 640x480 75.0 60.0 720x400 70.1 LVDS1 connected (normal left inverted right x axis y axis) 1280x800 60.2 + 1024x768 60.0 800x600 60.3 56.2 640x480 59.9 HDMI1 disconnected (normal left inverted right x axis y axis) DP1 connected (normal left inverted right x axis y axis) 1280x1024 75.0 60.0 1152x864 75.0 1024x768 75.1 60.0 800x600 75.0 60.3 640x480 75.0 60.0 720x400 70.1
I've submitted a bug report here: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/729788