evdev: Attach touchscreen to X screen

Stephan Josel s.josel at axis-simulations.at
Mon May 9 05:40:01 PDT 2011


We're trying to get a multi-touchscreen (multiple touchscreens not multi 
touch) setup working with the evdev driver in Ubuntu (Natty Narwhal, 
11.04). Basically, the touchscreens are configured and working except 
that the mapping to the correct X screen is wrong. We set up 5 
touchscreens in a row (Xorg ServerLayout "RightOf") with Xinerama 
enabled and their corresponding touchscreen inputdevices. Using xinput 
we are able to create a pointer for each of the touchscreens. The 
following is observed then: When touching any screen, the resulting 
movement of the pointer is only displayed on the first X screen (there 
are 5 pointers visible then on this screen). This is not at all the 
desired behavior. We would like to attach a touchscreen to a specific X 

Unfortunately, we found no way to tell the evdev driver to map a 
InputDevice to a X screen. Older versions of the driver provided an 
option "AbsoluteScreen" but the latest version hasn't anything like 
this. I know that the evtouch driver would provide a "ScreenNo" option, 
however evtouch is not available for Natty Narwhal. We also experimented 
with the Xorg coordinate transformation matrix, but with the result that 
the mouse movements where still on the first X screen.

So my question is:
How do I tell the evdev driver to map an InputDevice to a specific X 
screen? Is there an option line in xorg.conf or is there any method via 

Thanks in advance,

Stephan Josel
Software Engineer

AXIS Flight Training Systems GmbH
Philipsstrasse 27
8403 Lebring
Austria / Europe

Phone +43 (0)5 9889 -411
Fax   +43 (0)5 9889 -115


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