Disclaimer:

1. This instruction is for the Volla Tablet with Volla Pen Tiro. I have not tested this on any other device.

2. This fix only works for touch events and is a work-around until MIR support for pen input is fixed. Pressure sensitivity may come with MIR version 2.0 (roadmap this year) or never at all. Whenever there will be true pressure sensitivity the udev rules below have to be reverted / adjusted.

3. There is a bug in the libertine container (https://forums.ubports.com/topic/12135/input-events-in-right-third-of-screen-in-landscape-mode-are-not-registered-only-in-libertine-container If you want to use landscape orientation (as is normal when using the keyboard) there is no input in the right third of the screen which is annoying. The container works fine in portrait mode. In the above mentioned post you can also get an idea how handwriting looks like with touch input.

4. We have to write directly to the system partition, so installed libraries or udev rules might be overwritten with any update.

This instruction is working on ubuntu touch 24.01 stable with update version 437 (March 2026).

If you can live with the above - here is how to get the pen working. I will give detailed instructions, maybe other hardware / stylus combination may work in similar ways:

Make the system partition writeable:

sudo mount -o remount,rw /

Install the following packages:

sudo apt install evtest
sudo snap install libinput

find the input device: look for stylus, .... The Tiro Pen uses himax-stylus, make a note of the device identifier, e.g. himax-stylus. If there is no stylus: sorry, your journey ends here.

sudo snap run libinput.list-devices | grep Device
# for the Volla Pen Tiro:
# Device:        himax-stylus

output info regarding your stylus - replace himax-stylus with your pen. Also: it should have a line with Capabilities and Calibration. Note the event number (line starts with Kernel:)

sudo snap run libinput.list-devices | sed -n '/himax-stylus,+20p'
# Kernel:     /dev/input/event8

Are events registered? Replace with your event number, quit with Ctrl + c

sudo snap run libinput.debug-events --device /dev/input/event8   # Touch the screen with the pen
sudo evtest /dev/input/event8   # Pressure sensitity support? Press lighter and harder with the pen: do ABS_PRESSURE values change? 

If /dev/input/event8 exposes ABS_PRESSURE, and the device is (back) in tablet mode (ID_INPUT_TABLET=1, Capabilities: tablet), then the hardware/kernel side may already be capable of real pen pressure. In the Linux input model, ABS_DISTANCE is hover distance, while ABS_PRESSURE is the pressure axis; BTN_TOOL_PEN/ BTN_TOUCH describe pen presence and contact.

The output of

udevadm info -q property -n /dev/input/event8 | grep '^ID_INPUT'   # replace with nur event number

shows which mode the stylus is currently in:

• ID_INPUT_TABLET=1 (default): the pressure sensitive mode (if the stylus has the capability)
• ID_INPUT_TOUCHSCREEN=1: touch mode

ID_INPUT_TABLET=1: The driver actually reports pressure but MIR graphical surface is not reacting to it. No way to fix this. Let's switch to touch sensitivity (ID_INPUT_TOUCHSCREEN) so at least we get some events registered.

Let's use udev rules to remap the events: create a new rule

sudo nano /etc/udev/rules.d/99-himax-stylus-as-touch.rules

Redirecting input: Use your own stylus identifier from above, it is necessary to distinct this event from touch (hand) input and mouse events.

ACTION=="add|change", SUBSYSTEM=="input", KERNEL=="event[0-9]*", ATTRS{name}=="himax-stylus", \
  ENV{ID_INPUT}:="1", ENV{ID_INPUT_TABLET}:="", ENV{ID_INPUT_TOUCHSCREEN}:="1"

Apply the rule: reload udev and retrigger the device

sudo udevadm control --reload
sudo udevadm trigger /sys/class/input/event8   # replace with nur event number

Then verify:

udevadm info -q property -n /dev/input/event8 | grep '^ID_INPUT'
# it should list ID_INPUT_TOUCHSCREEN=1

you may need to restart the system. if it still says ID_INPUT_TABLET check your input. Test your pen with swiping from top or the left / right screen border.

To revert the rules: delete / comment the lines in the rules file and reboot.
If later on you want to test pressure sensitivity you can also switch to tablet mode with

ACTION=="add|change", SUBSYSTEM=="input", KERNEL=="event[0-9]*", ATTRS{name}=="himax-stylus", \
  ENV{ID_INPUT}:="1", ENV{ID_INPUT_TABLET}:="1", ENV{ID_INPUT_TOUCHSCREEN}:=""

and reload / retrigger:

sudo udevadm control --reload
sudo udevadm trigger /sys/class/input/event8   # replace with nur event number

I will write an instruction how to setup xournal++ app for handwriting later in another post.