A recent update of the xerver-xorg package (1:7.4+1) changed the way X configures input devices – they are now handled by hal or evdev, and their sections of the xorg.conf are ignored.

I filed a bug report, and was informed that it’s not a bug. I disagree, in that if you break things in an upgrade, it is a bug.

Never-the-less, I had to figure out how to get my EmulateWheel behaviour back since the upgrade.

The evdev man page is nigh on useless, but this blog entry helped a lot.  It has lead to the following as my /etc/hal/fdi/policy/marble_mouse.fdi:

<match key="info.product" string="Logitech USB Trackball">
 <merge key="input.x11_options.EmulateWheel" type="string">true</merge>
 <merge key="input.x11_options.EmulateWheelButton" type="string">8</merge>
 <merge key="input.x11_options.ZAxsisMapping" type="string">4 5</merge>
</match>

I got the info.product part by looking at /dev/input/by-id/, and
guessing. I logged out, and restarted hal for good measure. One or the
other may not be necessary.