Use at your own risk

A minimal PoC to switch Huion (Vendor ID 0x256C) devices into raw tablet mode. If successful this tool will print the following ouput on success:

HUION_MAGIC_BYTES=e7b480e280804ee1bfbfe18f98d883e8808004e0a1a3
HUION_FIRMWARE_ID=HUION_T21j_221221

Run via IMPORT in a udev rule to make the output udev properties on the device (see the Installing section below).

If successful, the tablet should send its events via the HID Report ID 0x8 (a 11 byte report on the Huion H641P).

This tool needs access to the device and thus needs to run as root:

$ sudo cargo build
$ sudo cargo run

$ cargo build
$ cp ./target/debug/huion-switcher /usr/lib/udev/
$ cp 80-huion-switcher.rules /etc/udev/rules.d

Then re-plug the device and udev will switch it to tablet mode on plug.