Synaptics touchpad driver synclient in Fedora 16 / Xorg with UDEV

I just installed Fedora 16 on an older IBM ThinkPad T42 laptop. Unfortunately, the two mouse buttons below the UltraNav touchpad just won’t work at all. Before opening up the case and fiddling around, I decided to try a software solution. Even after fairly exhaustive research, I couldn’t find anyone with a similar problem.

I did, however, find out that the synaptics touchpad driver has a synclient tool that can output the hardware events read directly from the input device. I tried running synclient -m 100 (to monitor hardware events every 100ms), but the only output that I got was Can't access shared memory area. SHMConfig disabled?. This was all a bit confusing to me, since Fedora 16 doesn’t even use an xorg.conf file. I was even more confused by a fair amount of information saying that SHMConfig is no longer used in synaptics 1.2+.

Long story short, the solution lies in /usr/share/X11/xorg.conf.d/50-synaptics.conf, which holds the synaptics config snippets for xorg. All you need to do is add the SHMConfig line before the end of the section:

Section "InputClass"
    Identifier "touchpad catchall"
    Driver "synaptics"
    ...
    Option "SHMConfig" "on"
EndSection

and then restart your X server. Now, running synclient -m should work fine.

I have to thank Red Hat’s Kevin Fenzi (nirik on #fedora on irc.freenode.org) for putting another set of eyeballs on the problem, and throwing out some ideas that finally led me to the solution.