dual head with Intel GM45 on Linux

With a new version of the kernel (2.6.28) and of Xorg (1.6.3), I am able to have a dual screen with my Intel GM45 graphics card. The monitors are plugged on the HDMI-1 and HDMI-2 ports of the docking station.

Note: you may be impacted by this bug.

the RandR way (recommended)

LVDS -> Dual head (docked)

You have to activate HDMI-1, desactivate LVDS, and then activate HDMI-2. Then you put HDMI-2 at the right of HDMI-1. I recommend arandr for this. If you don't desactivate LVDS , you will get the error: xrandr: cannot find crtc for output LVDS

To automate, here is a small shell script:


#!/bin/sh

xrandr --output HDMI-1 --auto

xrandr --output LVDS --off

xrandr --output HDMI-2 --auto

xrandr --output HDMI-2 --right-of HDMI-1

Dual head -> LVDS (before undocking)

To undock the laptop, first desactivate HDMI-2 and then activate LVDS. Here is a small script:


#!/bin/sh

xrandr --output HDMI-2 --off

xrandr --output LVDS --auto

xrandr --output HDMI-1 --off

the xorg.conf way

You can have dual head on startup with xorg.conf:


Section "Monitor"

       Identifier       "Monitor1"

       Option           "DPMS"

EndSection



Section "Monitor"

       Identifier       "Monitor2"

       Option "RightOf"  "HDMI-1"

       Option           "DPMS"

EndSection



Section "Device"

        Identifier  "intel"

        Driver      "intel"    

        Option "AccelMethod" "UXA" # with kernel > 2.6.28 and the new graphics stack of Linux (GEM memory management)   

        Option          "monitor-HDMI-1"  "Monitor1"

        Option          "monitor-HDMI-2"  "Monitor2"

        ## Note that LVDS is automatically switched off

EndSection