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[Bug 1078272] Re: It's impossible to configure multiple touchscreens using evdev


It is still a problem, partially.It  is possible to use coordinate
transformation matrix property (TransformationMatrix option in
InputClass section) to assign touchscreens to different displays, but
not to different X screens. But, unless system is SLI , or , or Mosaic
enabled - that is , it is supported by GPU and chipset -and that is
NVIDIA specific, then even with xinerama enabled every GPU is separate X
display. In that case , e.g, on x server :0 with screens :0.0, :0.1 and
0:0.2  even with proper matrix, mouse cursor simply jumps to bottom edge
of screen, if coordinates do not correspond to to :0.0 - i suspect it is
a bug on evdev side.

realistically that makes multiple touchscreen configuration possible
only with NVIDIA cards (twinview joins displays into one X screen), and
in case of 3 or more displays - only with SLI or BaseMosaic

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  It's impossible to configure multiple touchscreens using evdev

Status in “xserver-xorg-input-evdev” package in Ubuntu:

Bug description:
  We're trying to get a multi-touchscreen (multiple touchscreens not
  multi touch) setup working with the evdev driver in Natty Narwhal.
  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") 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 screen.

  Unfortunately, we found no way to tell the evdev driver to map a
  InputDevice to a X screen. Older versions of the driver (1.1.2)
  provided an option "AbsoluteScreen" (see
  http://manpages.ubuntu.com/manpages/dapper/en/man4/evdev.4.html)  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 xinput?

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