Configuring X for use with a laptop ALPS touchpad

Disclaimer: this information is available on an "AS-IS" bases.

I put my configuration here because mine and Markus' laptop shows slightly different input device layout... and in case you get it wrong, you can end with you keyboard blocked. For this is convenient:

• to make experiments with the laptop "hooked up" in a network,
• or with a serial console (so that you can kill X and restart)
• and have a copy of your original configuration file saved.

Basically, you have to enable the "event" input interface in X11; this will work only if the kernel has been compiled with the CONFIG_INPUT_EVDEV option enabled.

First of all, you have to determine which event interface is connected to the touchpad. Do a cat /proc/bus/input/devices/ and you'll see a thing similar to this:

I: Bus=0011 Vendor=0002 Product=0001 Version=0000
N: Name="PS/2 Generic Mouse"
P: Phys=isa0060/serio1/input0
H: Handlers=mouse0 event0 
B: EV=f 
B: KEY=420 0 670000 0 0 0 0 0 0 0 0 
B: REL=3 
B: ABS=1000003 

I: Bus=0011 Vendor=0001 Product=0001 Version=ab41
N: Name="AT Translated Set 2 keyboard"
P: Phys=isa0060/serio0/input0
H: Handlers=kbd event1 
B: EV=120003 
B: KEY=4 2000000 3802078 f840d001 f2ffffdf ffefffff ffffffff fffffffe 
B: LED=7 
    

In this case, in the fourth line you can see that the touchpad (which is the identified as a generic PS/2 mouse) can be read via mouse0 and event0 handlers. The "0" in "event0" is the key information you need.

Now, to the configuration file. Normally it is /etc/X11/XF86Config-4 (make a backup!). A copy of my XF86Config-4 file is here. The main things to notice are:

• In the ServerFlags section, assure yourself that the server will start even if any mouse problem is detected, listing the option AllowMouseOpenFail;
• Add the synaptic module adding a Load "synaptic" line to the "Module" section;
• Add the touchpad input device; if you look in my XF86Config-4 file it is the section that starts like:

    Section "InputDevice"
    Driver    "synaptics"
    Identifier   "alps"
    Option "Device"       "/dev/input/event0"
    Option "Protocol"     "event"
  

  Notice here the /dev/input/event0 line; this must coincide with the touchpad, otherwise weird things will happen. Notice again that in my laptop this is event0, and in Markus event1... so be careful.
• Finally, enable the touchpad as a complemetary core input device (so that the configuration will also work with a kernel with the event interface not enabled) with the two lines:

    InputDevice "alps" "AlwaysCore"
    InputDevice "mice" "CorePointer"
    
  

  in the ServerLayout section.

And don't forget to have a look at my gksyn applet!

Now, you can go back to the main Sony vaio page.