Wednesday, 21 January 2009

Fixing External monitors on the Aspire One and Fedora 10

I was recently forced to spend some time using my Aspire One as a primary development machine, having left my macbook PSU at work, and being too lazy to go all the way back in to retrieve it. 

So I thought, thats ok, I have this old monitor kicking around here, and a spare keyboard and mouse, just bang them into my Aspire One and off we go. But.......

Fedora 10 uses the new configless Xserver and the new Intel GEM enabled driver, a configless Xserver will happily run X without all the tedious fiddling with /etc/X11/xorg.conf. In fact if you take a peek in that directory you will see that there is no xorg.conf. 

So when I plugged my external monitor in, I was encouraged to see it display everything up to the login screen, logged in and was presented with a tiny 640x480 desktop on both monitors. 

Ok, no problem, pop up the Display properties dialog, set the sizes of the screens back to thier proper setup, 1024x600 for the builtin LCD, 1024x768 for the ext monitor. Press apply and ..... and .... and .... Nothing happened...  WHAT!!!!! 

OK it turns out that there is one vital piece of configuration that is missing in a configless Xserver boot, and thats the Virtual screen size.  You need a Virtual screen size that is bigger than the sum of both your monitor surfaces to run dual head (internal + external monitor). 

I tried everything, creating a minimal xorg.conf that just added that line, using sample xorg.confs for closely speced machines, nothing worked. And those that did, resulted in the disabling of DRI which produced syrupy screens on the external monitor. 

So the solution is to create an xorg.conf that is exactly what the autoconfig would produce, plus the extra line. 

So here are the steps

1. Reboot the Aspire and press RETURN when the initial bootloader screen comes up. 

2. press "a" and add a space then "3" to the end of the kernel boot line, press RETURN to boot the machine. 

3. The machine will boot to a command line instead of the usual graphical login screen. 

4. Login as root

5. Run the following

$cd /root
$Xorg -configure

The system will flash the screen and produce a file called in the current directory. This file contains all of the details that the configless startup would use.

$cp  /etc/X11/xorg.conf

Now locate the section at the end of that file that shows as below, and add the line indicated in

SubSection "Display"
Viewport        0 0
Depth     24
Virtual        2048 2048           # Add this line in 

6. Reboot the machine and you will now be able to reconfigure the monitors to support 1024x600 internal and 1024x768 external

Note: Because of limitations in the driver, if you use a value of more than 2048 in either dimension, it will disable DRI and the screen will become very slow again. This unfortunately limits the external display to 1024 width. If you want it to go wider then turn off the internal LCD panel in the Display Properties. This is being fixed in the next version of the driver, and this whole proceedure may become redundant by then as it will also support configless virtual spaces. 


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