mousetrap(1) is designed to be interposed between a nusb/kb(4) mouse
driver and the mouse event destination /dev/mousein, which provides an
opportunity to intercept the "raw" mouse events and transform them
before delivery to the rest of the system.
Example transformations include remapping and hooking up arbitrary actions to buttons, which is mainly useful for devices with more buttons than the Plan 9 recognizes. Yet another example might be filtering the pointer movement of overly sensitive devices.
If you plan on using this you are expected to modify the source code to suit your devices and needs. Some example mappings are provided to help with this.
mousetrap(1) can be installed into place, prior to running nusb/kb(4)
using the pipefile(1) utility as follows:
pipefile -r 'mousetrap -m elecom' /dev/mousein
nusb/kb 9
In the (near?) future filterfs(4) of some designation should be
replace pipefile(1) as a more Plan9esque filtering solution. Sigrid
of 9front works on this: https://git.sr.ht/~ft/filterfs
Figure out a satisfactory way to integrate this kind of device filtering
with the 9front boot mechanism. Currently the /sys/src/9/boot/nusbrc
has to be modified as per above and then a kernel has to be recompiled
and installed for it to take effect. We agree this kinds of sucks.
A temporary workaround, if you can get away with it, is kill(1)ing
the nusb/kb that got assigned to your device at boot and restarting
it manually. How to do this one is left as an exercise for the brave
reader. HINT: /dev/usbevent.