Xorg/xinput does not recognise evdev devices in Docker (Alpine base image) - docker

Question

I'm trying to run an Xorg server in Docker, due to the host OS not having any X installed, nor can it preserve installed packages between updates (however, Docker containers are preserved).
My goal is to run an X app in "kiosk" mode (no desktop environment, no window manager, just a single X app taking up the whole display), confined to the Docker container - specifically, Chromium to open the web management interface of the host (which is embedded in the distro).
After reading a swathe of Xorg/Xinput articles, setup guides, manuals and whatnot, and I'm still not sure what's going wrong.
This is my current Dockerfile:
FROM alpine:3.16
# Install Xorg
RUN \
apk add --no-cache \
xorg-server eudev mesa \
xinput xinit xhost evtest \
xf86-input-libinput xf86-video-fbdev xf86-input-evdev \
dbus xrandr xset xsetroot \
xeyes libinput mesa-dri-swrast mesa-dri-gallium mesa-egl
# Install Chromium
RUN \
apk add --no-cache \
chromium
CMD [ "/usr/bin/xinit", "/usr/bin/chromium-browser", "--no-sandbox", "--kiosk" ]
Then run it by passing in all the necessary udev entries:
docker run --rm -it \
--device=/dev/input \
--device=/dev/console \
--device=/dev/dri \
--device=/dev/fb0 \
--device=/dev/tty \
--device=/dev/tty1 \
--device=/dev/vga_arbiter \
--device=/dev/snd \
--cap-add=SYS_TTY_CONFIG \
alpine-xorg:latest http://172.17.0.1:8123/
In my case, I'm trying to use a 7" touchscreen HDMI display, designed for Raspberry Pis (however, I'm not using a Pi, but an Intel based mini PC).
Xorg logs aren't much help, they contain just init information about Xinput, no devices identified or anything.
Here's the log: https://paste-bin.xyz/65152
I've also fiddled around with evtest - in my case, /dev/input/event3 corresponds to the touchscreen's input, and evtest successfully recognises them: https://paste-bin.xyz/65154
However xinput doesn't even see these as a possible device:
a369b238e0f1:/var/log# xinput list
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
According to the Xorg logs, the appropriate init scripts have been loaded:
[ 3724.820] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
/usr/share/X11/xorg.conf.d/10-evdev.conf exists, and contains all the needed entries:
#
# Catch-all evdev loader for udev-based systems
# We don't simply match on any device since that also adds accelerometers
# and other devices that we don't really want to use. The list below
# matches everything but joysticks.
Section "InputClass"
Identifier "evdev pointer catchall"
MatchIsPointer "on"
MatchDevicePath "/dev/input/event*"
Driver "evdev"
EndSection
Section "InputClass"
Identifier "evdev keyboard catchall"
MatchIsKeyboard "on"
MatchDevicePath "/dev/input/event*"
Driver "evdev"
EndSection
Section "InputClass"
Identifier "evdev touchpad catchall"
MatchIsTouchpad "on"
MatchDevicePath "/dev/input/event*"
Driver "evdev"
EndSection
Section "InputClass"
Identifier "evdev tablet catchall"
MatchIsTablet "on"
MatchDevicePath "/dev/input/event*"
Driver "evdev"
EndSection
Section "InputClass"
Identifier "evdev touchscreen catchall"
MatchIsTouchscreen "on"
MatchDevicePath "/dev/input/event*"
Driver "evdev"
EndSection
Where is this setup going wrong, why can't xinput register the evdev devices when the necessary events are clearly there and usable?