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.

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:

2:2.13.901-2ubuntu2~xup~maverick

xrandr output

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