Fixing C720 Trackpad in Xubuntu 14.04

While trying to use Xubuntu 14.10 Utopic Unicorn, the trackpad isn’t supported by default. I followed the lead of a reddit thread which suggested upgrading to a newer kernel. Ubuntu just happens to provide the latest kernels, you just have to know where to find them. I cropped the recommended URL in the reddit thread to just http://kernel.ubuntu.com/~kernel-ppa/mainline/, which displays all the latest deb releases of kernels and then names them for the release using the codename.

When I wrote this blog post, the latest 3.17 kernels for 14.10 were at:

Ignore the low latency kernel options unless audio production is important to you. Just dpkg -i *.deb those files, reboot, and it should hopefully fix your C720 trackpad when you boot Ubuntu variants from a USB drive. Also ignore 3.18-rc2 - that wouldn’t boot my cryptfs.

The default sensitivity settings stink, so create a file at /usr/share/X11/xorg.conf.d/50-cros-touchpad.conf:

Section "InputClass"
    Identifier      "touchpad peppy cyapa"
    MatchIsTouchpad "on"
    MatchDevicePath "/dev/input/event*"
    MatchProduct    "cyapa"
    MatchIsTouchpad "on"
    Option "TapButton1" "1"
    Option "TapButton2" "3"
    Option "TapButton3" "2"
    Option "MaxTapMove" "20"
    Option "MaxTapTime" "140"
    Option "ClickTime" "5"
    Option "FingerHigh" "12"
    Option "FingerLow" "10"
    Option "LockedDrags" "true"
    Option "LockedDragTimeout" "100"
    Option "ClickFinger1" "1"
    Option "ClickFinger2" "3"
    Option "ClickFinger3" "2"
    Option "SingleTapTimeout" "140"
EndSection

See also: https://web.archive.org/web/20150315075554/http://www.reddit.com/r/chrubuntu/comments/1rsxkd/list_of_fixes_for_xubuntu_1310_on_the_acer_c720/