DisplayLink

DisplayLink is a technology that enables monitors to work via USB.

Kernel
There are two drivers that could be used (as of Linux kernel 3.4) :
 * udl - is newer and working on 3D acceleration
 * udlfb - the original driver with working 2D support

Enable the DisplayLink framebuffer device in your kernel:

After booting into the new kernel the external monitor should show a green background image. That means the kernel module is loaded and the device works, it also creates the device in /dev/fb0.

To check which driver is loaded (udl or udlfb):

If you do not want to use the newer one or have problems, prevent it from loading:

X11 Driver
For X11 drivers, you can use or x11-drivers/xf86-video-displaylink from the x11 overlay (needs Layman installed).
 * xf86-video-fbdev


 * xf86-video-displaylink

One X-Server
TODO

Two X-Server
This method is failsafe and should work with any graphics card installed. We start two instances of X-Server for each device and then use a software called x2x to move the input devices between them.
 * two independent instances and desktops
 * Input devices follow the mouse pointer

Software
For this method, we need another input device driver called :

The program is available in portage and can be installed via:

xorg.conf.DL
We configure two independent /etc/X11/xorg.conf for each device and initialize the desktop using ~/.xinitrc scripts. Create this file in /etc/X11/ and name it xorg.conf.DL:

.xinitrc2
Next we create the ~/.initrc2 for our external display. Create and customize the file to your needs, here is an example:

displaylink.sh
This is the actual script that starts the second instance of xorg-server. Make it executeable and save it somewhere in your home folder, in this example we save it to ~/.displaylink.sh

External resources

 * libdlo freedesktop.org
 * Linux Forum displaylink.org
 * Linux plugable.com
 * Setting up Multiseat plugable.com