Comment 14 for bug 1629613

Updating BIOS managed to improve the situation to the point where I can consistently make the touchpad work, although it is inconvenient.

Laptop: Dell XPS 13 Developer Edition (9333)
OS: 16.04 LTS - updated from 14.04 LTS - updated from 12.04 LTS, which was the original OS and had touchpad working.

Here's how I "made" it work.

1. Updated BIOS from A02 to A08 (latest for my model) - as per Dell's instructions[0].
2. After reboot, `xinput` output finally had "SynPS/2 Synaptics TouchPad", BUT it was still not responsive.
3. `sudo apt-get install evtest` (required for step #4).
4. Following the "Debugging Touchpad Detection"[1] I switch to VT (CTRL+ALT+F2)
5. Run `cat /proc/bus/input/devices` I find the touchpad name is `event5`.
6. Run `sudo evtest /dev/input/event5 > event` and do various gestures on the touchpad, then CTRL+C.
7. Switch back to X (CTLR+ALT+F7) - turns out the touchpad is now working.

After rebooting touchpad is non-responsive, but if I repeat steps 6 & 7 - it starts working again. I'm not sure if this is reproducible on other models, but I hope this is helpful for further debugging.

[0]: http://www.dell.com/support/Article/us/en/04/SLN284433/en
[1]: https://wiki.ubuntu.com/DebuggingTouchpadDetection#In_case_your_Touchpad_doesn.27t_work_at_all_.28No_response_from_the_Touchpad.29