I couldn't find anything for Linux on the synaptics website, but I found
I emerged this, and then build the evdev kernel module and loaded it. I then changed my xorg.conf to use protocol "auto-dev", as it says. However, when I started X, it went to a blank screen, which I couldn't leave. I force-shut down my laptop, and started again and looked at the Xorg.0.log, which said that auto-dev was not a valid protocol.
EDIT: I think that the module I got off Portage was for XFree86, so the next step is to remove the ebuild and build it myself.
EDIT: It seems that I don't have the correct X includes to build it for Xorg, so it's build for XF86. Where can I get them?