Udev rule to automatically disable touchpad when a USB mouse is connected

Question

I am pretty new to udev and wanted to write a rule that upon connecting an usb mouse disables my touchpad.

This is what I have come up with(mostly by ear):

ACTION=="add", SUBSYSTEM=="input", ENV{ID_MODEL}=="USB_Mouse", ENV{DISPLAY}=":0", ENV{XAUTHORITY}="/home/nikitautiu/.Xauthority", ENV{REMOVE_CMD}="/usr/bin/synclient TouchpadOff=0", RUN+="/usr/bin/synclient TouchpadOff=1"

Nonetheless it doesn't trigger the desired effect. The command seems to be fine though the rule does not trigger when connecting my usb mouse.

Answer 1

I don't grasp why your rule is so complex? Especially this section

ENV{ID_MODEL}=="USB_Mouse",\
ENV{DISPLAY}=":0",\
ENV{XAUTHORITY}="/home/nikitautiu/.Xauthority",\   
ENV{REMOVE_CMD}="/usr/bin/synclient TouchpadOff=0"

In the first line you match the environment variable ID_MODEL which is only seen by udev against USB_Mouse. In the following three lines you assign values to environment variables. Again only seen by udev and the executed command synclient if the rule is applied.

I'm pretty sure that this rule is never applied (You can check this by parsing udev's log file.) since it is likely that there is no variable ID_MODEL with content USB_Mouse accessible unless you set ID_MODEL in the udev environment previously.

I suggest that you match against the Action, the vendor-ID and the product-ID of your mouse, which will suffice in most cases. Then your rule looks like

ACTION=="add", ATTRS{idVendor}=="<idVendor>", ATTRS{idProduct}=="<idProduct>", RUN+="/usr/bin/synclient TouchpadOff=1"

You can get <idVendor> and the <idProduct> by parsing the output of

lsusb -v

I don't remember if the given hex-values are allowed in the classical form 0xffff. I always take only the part behind 0x in my rules.

Answer 2

Since the accepted answer doesn't work on my system here is a udev rule that works with gnome/gdm v. 3.16.2 and udev/systemd v. 226:

ACTION=="add", ATTRS{bInterfaceProtocol}=="02", ATTRS{bInterfaceClass}=="03", \
ATTRS{bInterfaceSubClass}=="01", ENV{XAUTHORITY}="/run/user/1000/gdm/Xauthority", \
ENV{DISPLAY}=":0", ENV{REMOVE_CMD}="/usr/bin/xinput --enable 'SynPS/2 Synaptics TouchPad'", \
RUN+="/usr/bin/xinput --disable 'SynPS/2 Synaptics TouchPad'"

ENV{REMOVE_CMD} is the command used when the device is removed.
SynPS/2 Synaptics TouchPad is the name of the touchpad device as reported by xinput.
The UID used in ENV{XAUTHORITY} (e.g. 1000 in my rule) has to match your user ID.
Note the backslashes at end of lines are needed, as otherwise udev rules cannot span over multiple lines. If you prefer in one line:

 ACTION=="add", ATTRS{bInterfaceProtocol}=="02", ATTRS{bInterfaceClass}=="03", ATTRS{bInterfaceSubClass}=="01", ENV{DISPLAY}=":0", ENV{XAUTHORITY}="/run/user/1000/gdm/Xauthority", ENV{REMOVE_CMD}="/usr/bin/xinput --enable 'SynPS/2 Synaptics TouchPad'", RUN+="/usr/bin/xinput --disable 'SynPS/2 Synaptics TouchPad'"

Answer 3

Given another answer that works on KDE (plasma, sddm).

I added the rule filename /etc/udev/rules.d/61-touchpadoff.rules with the following content:

ACTION!="add", GOTO="touchpadoff_end"

KERNEL=="mouse[0-9]", SUBSYSTEM=="input", SUBSYSTEMS=="usb", ENV{DISPLAY}=":0", ENV{REMOVE_CMD}="/usr/bin/xinput --enable 'Elan TouchPad'", RUN+="/usr/bin/xinput --disable 'Elan TouchPad'"

LABEL="touchpadoff_end"

You need to thange the name of your touchpad hardware. To see it issue a command % xinput --list

I hope this helps you KDE-heads.