To use an independent mouse for each of your independent X servers/sessions, you just have to modify the input section of the XFree configuration files to point to the proper device files.
Use /dev/input/mouse[n], where n is the number of your mouse starting from 0:
1st mouse --> /dev/input/mouse0
2nd mouse --> /dev/input/mouse1
3rd mouse --> /dev/input/mouse2
4th mouse --> /dev/input/mouse3
You shouldn't use /dev/input/mice because it merges the input from all mouse devices.
Here is my configuration before modifications:
------------------------------------------------------------------------------------------------
# **********************************************************************
# Pointer section
# **********************************************************************
Section "InputDevice"
Identifier "Mouse1"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/psaux"
Option "ZAxisMapping" "4 5"
# ChordMiddle is an option for some 3-button Logitech mice
Option "Emulate3Buttons"
# Option "ChordMiddle"
EndSection
------------------------------------------------------------------------------------------------
|
After modifications for the first X server:
------------------------------------------------------------------------------------------------
# **********************************************************************
# Pointer section
# **********************************************************************
Section "InputDevice"
Identifier "Mouse1"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mouse0"
Option "ZAxisMapping" "4 5"
# ChordMiddle is an option for some 3-button Logitech mice
Option "Emulate3Buttons"
# Option "ChordMiddle"
EndSection
-----------------------------------------------------------------------------------------------
|
For the second X server:
-----------------------------------------------------------------------------------------------
# **********************************************************************
# Pointer section
# **********************************************************************
Section "InputDevice"
Identifier "Mouse1"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mouse1"
Option "ZAxisMapping" "4 5"
# ChordMiddle is an option for some 3-button Logitech mice
Option "Emulate3Buttons"
# Option "ChordMiddle"
EndSection
-----------------------------------------------------------------------------------------------
|
and so on ...