Enable MultiTouch for Synaptics Touchpad on Debian

Data for this was found primarily in the first link below. It took a while to get it working until I found the 2nd link.

• http://techdigger.wordpress.com/2009/04/02/multitouch-on-synaptics-trackpad-on-linux/ - xorg.conf config info
• http://groups.google.com/group/linux.debian.user/browse_thread/thread/98cb32d263ba5501 - SHMConfig requires ServerLayout section in xorg.conf

Your xorg.conf must use the synaptics driver with some options for InputDevice and must contain a ServerLayout section:

Section "ServerLayout"
	Identifier	"Default Server Layout"
	Screen		"Default Screen"
	InputDevice	"Generic Keyboard"	"CoreKeyboard"
	InputDevice	"Synaptics Touchpad"	"CorePointer"
EndSection

Section "InputDevice"
	Identifier	"Synaptics Touchpad"
	Driver		"synaptics"
	Option		"SendCoreEvents"	"true"
	Option		"Device"		"/dev/psaux"
	Option		"Protocol"		"auto-dev"
	Option		"HorizScrollDelta"	"0"
	Option		"SHMConfig"		"on"
	Option		"HorizEdgeScroll"	"on"
	Option		"VertEdgeScroll"	"on"
	Option		"VertTwoFingerScroll"	"on
	Option		"HorizTwoFingerScroll"	"on"
	Option		"CornerCoasting"	"on"
	Option		"PalmDetect"		"on"
	Option		"CircularScrolling"	"on"
	Option		"CircScrollTrigger"	"3"
EndSection

Restart X and run test it out by dragging two fingers on your touchpad. You can debug it with:

synclient -m 100

Sample output below. the f column is the number of fingers it senses. The bold parts show a successful vertical scroll.

   time     x    y   z f  w  l r u d m     multi  gl gm gr gdx gdy
  0.414     1 5855   2 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  0.514     1 5855   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0
  0.714     1 5855   1 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  0.814     1 5855   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0
  2.115  4032 3273  23 1  8  0 0 0 0 0  00000000   0  0  0   0   0
  2.215  3967 3252  91 1  9  0 0 0 0 0  00000000   0  0  0   0   0
  2.316  3945 3043  94 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  2.416  3921 2583  94 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  2.516  3887 2160  94 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  2.616  3858 1754  94 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  2.716  3851 1704  94 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  2.816  2449 1539   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0
  2.916     1 5855   1 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  3.016     1 5855   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0
  3.216     1 5855   1 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  3.316     1 5855   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0
  3.416     1 5855   1 2  5  0 0 0 0 0  00000000   0  0  0   0   0
  3.517     1 5855   0 0  0  0 0 0 0 0  00000000   0  0  0   0   0

If you get this error:

Can't access shared memory area. SHMConfig disabled?

You may be missing the ServerLayout reference to CorePointer.