Unofficial Kinesis Freestyle 2 Userspace Linux Driver

SECURITY NOTICE: This program should not run as root! Read the Install instructions for details on how to set the correct permissions on the device files that the driver opens so that it can do so with normal user permissions.

The Kinesis Freestyle 2 keyboard is a fantastic split keyboard for people who don't want RSI in their wrists. It has four multimedia keys on F8-F11 that do not work in Linux. This is a simple program that enables those keys. If you care how it works, keep reading. If not, skip to the Build instructions.

I spent a weekend digging into how this keyboard sent input for these multimedia keys. I documented the process in a series of blog posts:

• Part 1 - Debugging the problem
• Part 2 - Fix it in userspace
• Part 3 - Permissions
• Part 4 - Automation

kfreestyle2d itself only depends on the Linux kernel. If you run Linux with uinput version 4 or later, you should be fine.

The automatic execution of kfreestyle2d currently depends on udev and systemd. If you run a system that uses a different init system or device manager, we'd love some help with automatic installation procedures on those systems.

The multimedia keys seem not to be understood properly by the hid-generic kernel module that usually interprets events from HID (Human Interface Devices). They are understood by the hidusb kernel module though, so you can read the raw HID file to get the stream of bytes coming from the USB device.

This program uses a special kernel interface called uinput that allows drivers for input devices to run as user programs. kfreestyle2d simply opens the raw byte stream from the keyboard's special function keys. When it reads a keypress, it translates the HID Usage ID of the key that it read into a keypress that the uinput system understands. This allows the kernel to interpret the keypress correctly and dispatch it to userspace programs like Xorg properly.

make will create the binary kfreestyle2d in the current directory. If you want to try it without installing it, skip to the Manual Run section below.

Please check the makefile before installing. You may wish to adjust the value of PREFIX or one of the other macros.

To properly install kfreestyle2d, you should be able to simply run sudo make install. This will:

• Create a directory (default is /usr/local/share/kfreestyle2d) to store the executable and script.
• Create some udev rules in /etc/udev/rules.d/99-kfreestyle2d.rules
• Create a new systemd service file in /etc/systemd/system/kfreestyle2d.service

Once those things are done, the driver should run automatically when you plug in the keyboard and should stop when you unplug it. If you have any problems running this command, please open an issue.

Please note that the current setup only supports one Kinesis Freestyle 2. If you want to plug multiple Kinesis Freestyle 2 keyboards into the same computer, you'll need to customize the automatic execution accordingly.

This procedure will work to test whether the userspace driver is working without the udev and systemd automation in place. If you already followed the Install directions, you shouldn't need to do this.

First, ensure that the uinput kernel module is loaded with lsmod | grep uinput. If that does not return a line containing uinput, run sudo modprobe uinput to load the userspace input module into your kernel.

The driver expects to be given the path to an HID raw input device that corresponds to the special function keys of a Kinesis Freestyle 2.

To find the correct HID raw input device, unplug your keyboard and ls /dev/hidraw*. Then plug it in and ls /dev/hidraw*.

There should be two new /dev/hidrawX files the second time.

Try sudo head -c 1 /dev/hidrawA where A is the first new raw input file. Then type on your keyboard. If the command exits, it just read normal keyboard input from that file, which means that it is not the special function key raw input file. If the command does not exit, try typing one of the special keys (mute, volumedown, volumeup, calculator). Remember to press the function key before trying to use these. If the command exits when you type a special key, this is the file you're looking for.

To start the driver, run: ./kfreestyle2d /dev/hidrawX where X is the number of the raw input device for the special keys.

When the driver is running, it should create a new /dev/input/eventXX file, where XX is some number with 1-3 digits. You can run sudo evtest /dev/input/eventXX on that file to see the output generated by the driver when you press those keys.

If the driver isn't generating output, feel free to create an issue.

If it is, you should now be able to configure your programs to handle these keys using ordinary X or Wayland key configuration.

Suggestions and PRs welcome!