Logitech Wireless Touchpad under Debian Jessie

Wed, Nov 9, 2016

This is a cheap but useful and well-built touchpad. It has nice rubber feet and is heavy enough to rest really well on the desk. It takes two AA batteries that supposedly power it for months. It connects wirelessly (hence the name) to a /unifying/ receiver, which is a tiny usb adapter.

This thing is fully supported in Linux - out of the box! Pointing, tap to click, scrolling by two-finger swipe and the (physical) buttons just work! However, at least under Debian Jessie, you need to do more if you wish to have gestures like “two finger tap” means “right click” and “three finger tap” means “middle click”.

Install a more recent kernel

If you are using the stock 3.16 kernel, you are missing an essential driver, and the touchpad will fall back in some sort of compatibility mode. More recent kernels (why not use 4.8 or newer?), include the required driver, which implements the protocol spoken between touchpad and unifying receiver. It is called hid_logitech_hidpp, and the Linux kernel option HID_LOGITECH_HIDPP needs to be enabled.

Configure Xorg to use the synaptics driver

Once you have a kernel that can speak the correct protocol, the touchpad acts as a synaptics touchpad, which enables it to emit all the gestures that synaptics touchpads offer. These include the right click and middle click.

You need to add the following into a file /etc/X11/xorg.conf.d/70-synaptics.conf:

Section "InputClass"
  Identifier "touchpad catchall"
  Driver "synaptics"
  MatchIsTouchpad "on"
  MatchDevicePath "/dev/input/event*"
  Option "TapButton1" "1"
  Option "TapButton2" "2"
  Option "TapButton3" "3"
  Option "VertEdgeScroll" "off"
  Option "VertTwoFingerScroll" "on"

Boot the new kernel and enjoy your touchpad

Now you can fiddle with your touchpad even more using the configuration dialogs of your favourite desktop environment, or directly using the xinput and synclient tools.

First, find out the number of your touchpad:

$ xinput

Then you can list all available settings:

$ xinput list-props $number_of_your_device

And change them as you like:

$ xinput set-prop $number_of_your_device "Evdev Wheel Emulation" 1

Have fun!

Tags: linux

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