Comment 23 for bug 512192

This looks to be a duplicate of https://bugs.launchpad.net/ubuntu/+source/linux/+bug/418282

They also tried disabling the check I mentioned in my last post and had similar results. I also tried forcing version 2.

With these modifications to elantech.c, dmesg says:
elantech.c: assuming hardware version 2, firmware version 4.17

If debugging is then enabled by:
sudo sh -c "echo 2 > /sys/bus/serio/drivers/psmouse/serio4/debug"

(serio4 was determined by dmesg | grep Elantech the number may vary on other systems)

...and then watch the output of syslog while messing with the touchpad:
tail -f /var/log/syslog | grep elantech.c

The packets do not seem to match the "Native absolute mode 6 byte packet format" described in:
http://www.kernel.org/doc/Documentation/input/elantech.txt

As far as I can gather, this is what the first byte looks like for these touchpads:

76543210
11100100 three fingers 0xE4
10000100 two fingers 0x84
01010100 thumb 0x54
01000100 one finger 0x44
00001000 no finger 0x04

x and y aren't at all obvious to me, I haven't got a clue about the other 5 bytes.