Ubuntu – How to add display resolution for an LCD in Ubuntu 12.04? xrandr problem

I am new to Ubuntu. I have installed Ubuntu 12.04 and am stuck trying to set up the correct resolution for my LCD display.

The native resolution for the LCD is 1920×1080

here is the output from xrandr:

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 720, maximum 4096 x 4096
LVDS1 connected 1280x720+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
1280x720 60.0*+
800x600 60.3 56.2 
640x480 59.9
VGA1 disconnected (normal left inverted right x axis y axis)

Then I create new modeline:

$ cvt 1920 1080 60
1920x1080 59.96 Hz (CVT 2.07M9) hsync: 67.16 kHz; pclk: 173.00 MHz
Modeline "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync

So far so good. Then I create new mode using xrandr:

$ xrandr --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync

But for some reason that new mode was created for VGA (VGA1) output instead of LCD output (LVDS1):

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 720, maximum 4096 x 4096
LVDS1 connected 1280x720+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
1280x720 60.0*+
800x600 60.3 56.2 
640x480 59.9 
VGA1 disconnected (normal left inverted right x axis y axis)
1920x1080_60.00 (0xbc) 173.0MHz <---------- ????!!!!!!
h: width 1920 start 2048 end 2248 total 2576 skew 0 clock 67.2KHz
v: height 1080 start 1083 end 1088 total 1120 clock 60.0Hz

So, if I try to add mode to LVDS1, I get an error:

$ xrandr --addmode LVDS1 "1920x1080_60.00"
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 149 (RANDR)
Minor opcode of failed request: 18 (RRAddOutputMode)
Serial number of failed request: 25
Current serial number in output stream: 26

Adding that new mode to VGA1 works fine, but I don't use that VGA1 output.