Q:

Where to put X11 drivers configuration in Ubuntu Lucid?

Since hal is removed from Lucid, where now can I put all those little configuration tweaks for mouse and other input devices? 
In particular, I want to configure ThinkPad trackpad to enable scrolling with middle button. In hal, it was done with 
<match key="info.product" string="TPPS/2 IBM TrackPoint">
    <merge key="input.x11_options.EmulateWheel" type="string">true</merge>
    <merge key="input.x11_options.EmulateWheelButton" type="string">2</merge>
    <merge key="input.x11_options.ZAxisMapping" type="string">4 5</merge>
    <merge key="input.x11_options.XAxisMapping" type="string">6 7</merge>
    <merge key="input.x11_options.Emulate3Buttons" type="string">true</merge>
    <merge key="input.x11_options.EmulateWheelTimeout" type="string">200</merge>
</match>

A:

I've managed to find the right place. It's /usr/lib/X11/xorg.conf.d/. There's already some configuration files that can be used as examples but surprisingly man xorg.conf have good enough documentation about all new Match keywords.
The example from the post can be translated to the following snippet (in a file /usr/lib/X11/xorg.conf.d/20-trackpoint.conf)
Section "InputClass"
    Identifier      "Trackpoint"
    MatchProduct    "TPPS/2 IBM TrackPoint"
    MatchDevicePath "/dev/input/event*"
    Option          "EmulateWheel" "true"
    Option          "EmulateWheelButton" "2"
    Option          "ZAxisMapping" "4 5"
    Option          "XAxisMapping" "6 7"
    Option          "Emulate3Buttons"   "true"
    Option          "EmulateWheelTimeout" "200" 
    Option          
EndSection

Note: for Ubuntu 10.10 you should place your config files in /usr/share/X11/xorg.conf/ instead.

