I finally got the Alps touchpad working on a Dell N5110. Briefly, it's a new protocol to init the device and the 6-byte packets coming from it are a new format. I didn't spend much time trying to understand the init sequence, just stuck the qemu packet dump into a new (V6) init function. But it works; probably needs to be tightened up a little. I don't understand the thought process behind the different protocols. It seems like the NRE to keep writing test and production drivers would be unsustainable.
I created a psmouse DLKM with a README at . If there's anybody else with an N5110 who wants to try it out please post your results.