Touchpad on Thinkpad T400s doesn't support two-finger scroll

Binary package hint: xserver-xorg-input-synaptics

The touchpad on my laptop (a thinkpad T400s) supports recognising more than one finger hardware-wise, but that doesn't work under Ubuntu currently. In the touchpad capplets, I can only select the edge scrolling option, not the two-finger scrolling option.

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: xserver-xorg-input-synaptics 1.2.2-2ubuntu5
ProcVersionSignature: Ubuntu 2.6.35-22.33-generic 2.6.35.4
Uname: Linux 2.6.35-22-generic x86_64
Architecture: amd64
DRM.card0.DisplayPort.1:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.DisplayPort.2:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.DisplayPort.3:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.HDMI_Type_A.1:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.HDMI_Type_A.2:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
DRM.card0.LVDS.1:
 status: connected
 enabled: enabled
 dpms: On
 modes: 1440x900
 edid-base64: AP///////wAwrjZAAAAAAAASAQOAHhN46uWVk1ZPkCgoUFQAAAABAQEBAQEBAQEBAQEBAQEBwSmg5FGEGjAwIDYAL74QAAAZ3iKgLFGEfjAwIDYAL74QAAAZAAAADwCVCjKVCigeCQBMo0JUAAAA/gBMVE4xNDFCVDA4MDAxAMs=
DRM.card0.VGA.1:
 status: disconnected
 enabled: disabled
 dpms: Off
 modes:
 edid-base64:
Date: Mon Sep 27 12:14:07 2010
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429)
MachineType: LENOVO 28239KG
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35-22-generic root=UUID=7b361d96-9c1b-4168-b7b1-261e6bd2734d ro quiet splash
ProcEnviron:
 LANG=en_DK.utf8
 SHELL=/bin/bash
SourcePackage: xserver-xorg-input-synaptics
dmi.bios.date: 05/31/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 6HET30WW (1.15 )
dmi.board.name: 28239KG
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr6HET30WW(1.15):bd05/31/2010:svnLENOVO:pn28239KG:pvrThinkPadT400s:rvnLENOVO:rn28239KG:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 28239KG
dmi.product.version: ThinkPad T400s
dmi.sys.vendor: LENOVO
system:
 distro: Ubuntu
 codename: maverick
 architecture: x86_64
 kernel: 2.6.35-22-generic

This turns out to be a combination of several issues:

The kernel driver likely does not have a driver for the touchpad which supports multiple fingers. The touchpad however does support reporting fingerwidth and can therefore be used with two-finger emulation.

Two-finger emulation cannot be turned on using the Gnome Mouse capplet. See Gnome bug #625163

Even if one turns on two-finger emulation using the xinput interface, two-finger scrolling does not work. This is because, on Ubuntu, the default value for the property "Synaptics Two-Finger Pressure" is 280, which is much too high. A Fedora 14 Live CD i booted for testing, had a default value of 29 for that property. Indeed, lowering that value under Ubuntu makes Two-finger scrolling work. See the upstream bug for more info.

I don't know why this pressure default value is wrong on Ubuntu. It could be due do a different synaptics version, or due to a patch in Ubuntu?

I think this is more a duplicate of bug #849461 just changing the one synaptics configuration variable makes it work on my T400...