Using a cheap Bluetooth Sheet Music Pedal on Linux

I recently (as in, half a year ago) bought a cheap Bluetooth sheet music pedal from AliExpress. I expected it to work out of the box, since it’s just a fancy Bluetooth keyboard with only two keys. Which it did for Android, but not for Linux; pressing the buttons did exactly nothing.

Turns out its vendor ID is 05AC, which belongs to Apple: They probably use it to make pairing the pedal to iPads seamless.

Short side note: iPads are the de facto standard for sheet music tablets, not because of the (to be fair, very good) hardware, but because there simply isn’t anything as good as forScore for Android (yet!).
But I don’t care about that! I just want to rotate my laptop 90° and read sheet music in Okular.

The problem turns out to be hid-apple, the hid driver for Apple’s own keyboards and mice, claiming the device.

[ 109.322607] apple 0005:05AC:022C.0006: Fn key not found (Apple Wireless Keyboard clone?), disabling Fn key handling
[ 109.322798] input: P2 Smart Pedal as /devices/virtual/misc/uhid/0005:05AC:022C.0006/input/input24
[ 109.380802] apple 0005:05AC:022C.0006: input,hidraw3: BLUETOOTH HID v1.1b Keyboard [P2 Smart Pedal] on 04:7b:cb:b9:45:57

The solution is to manually unbind it from hid-apple and binding it to hid-generic. One caveat: We must tell hid-generic to accept devices with special drivers, otherwise it will just claim "No such device" (which, as you can probably imagine, was very frustrating when trying to solve this)

echo 0005:05AC:022C.000x > /sys/bus/hid/drivers/apple/unbind
echo 1 > /sys/module/hid/parameters/ignore_special_drivers
echo 0005:05AC:022C.000x > /sys/bus/hid/drivers/hid-generic/bind

Because I don’t want to manually re-bind the pedal on every connect, here’s my udev rule:

ACTION=="bind", SUBSYSTEM=="hid", KERNEL=="0005:05AC:022C.*", RUN+="/bin/sh -c 'echo %k > /sys/bus/hid/drivers/apple/unbind; echo 1 > /sys/module/hid/parameters/ignore_special_drivers; echo %k > /sys/bus/hid/drivers/hid-generic/bind'"

Put that line in /etc/udev/rules.d/99-smart-pedal.rules and reload with sudo udevadm control --reload-rules, after which the pedal should work.