Host evidence: the virtual device is classified as a touchpad

Class: host build / host uinput device creation. Run on the development host (x86_64-linux), not the K230 board. This proves the ioctl sequence in nix/touch-trackpad/src/uinput.rs produces a device Linux’s own udev classifier calls a touchpad; it does not prove libinput/Sway behave correctly with the real GT9895 driving it, or that gestures work on glass. That remains board evidence, gated in tasks.md.

Command

cd nix/touch-trackpad
K230_TT_SMOKE_SLEEP_SECS=6 cargo test creates_and_destroys -- --nocapture --test-threads=1 &
sleep 3
for p in /sys/class/input/event*; do
  name=$(cat "$p/device/name" 2>/dev/null)
  if [[ "$name" == *"k230-touch-trackpad-test"* ]]; then
    echo "found: $p ($name)"
    udevadm info --query=property --path="$p"
  fi
done
wait

(K230_TT_SMOKE_SLEEP_SECS was a temporary env-gated sleep added to the creates_and_destroys_a_real_virtual_touchpad_if_permitted test for this one capture, then reverted — the committed test creates and immediately destroys the device, as normal.)

Result

found: /sys/class/input/event24 (k230-touch-trackpad-test)
DEVPATH=/devices/virtual/input/input37/event24
DEVNAME=/dev/input/event24
MAJOR=13
MINOR=88
SUBSYSTEM=input
USEC_INITIALIZED=513569911194
ID_INPUT=1
ID_INPUT_TOUCHPAD=1
ID_SERIAL=noserial

ID_INPUT_TOUCHPAD=1 is udev’s own 60-input-id builtin classifier (the same mechanism libinput’s udev-backed device enumeration in Sway consults), set from exactly the bits uinput.rs’s VirtualTouchpad::create declares: EV_KEY capability including BTN_TOOL_FINGER + INPUT_PROP_POINTER/INPUT_PROP_BUTTONPAD, with INPUT_PROP_DIRECT never set. No ID_INPUT_TOUCHSCREEN property appears.

Also covered by this same host run

cargo test (20/20 passing, see nix/touch-trackpad/src/*.rs #[cfg(test)] modules):

relay.rs: the protocol-translation state machine against synthetic 1/2/3-finger event sequences (tap, drag, lift, 2-to-1-finger transition).
mode.rs: DRM-sysfs-fixture-driven mode detection (panel-only, HDMI connected, HDMI present-but-unplugged, missing/absent DRM root).
devsearch.rs: /proc/bus/input/devices stanza parsing against a fixture containing the real recorded device name (“Goodix Berlin Capacitive TouchScreen”, from docs/evidence/touch-evtest.txt).
uinput.rs: every UI_*/EVIOCGRAB/EVIOCGABS ioctl number independently hand-computed and checked against the kernel’s own linux/uinput.h/linux/input.h macro expansions, plus the two on-wire struct sizes (uinput_setup = 92 bytes, uinput_abs_setup = 28 bytes).

cargo clippy --all-targets: clean (0 warnings) after fixing one collapsible_if lint.