default composite device grabs kernel touchpad on non-Deck hardware, blocking libinput

[wzzfather]

Touchpad source is unconditionally grabbed by the default CompositeDevice, blocking libinput/host access

Summary

On Bazzite-Deck (SteamOS-style input stack), InputPlumber v0.79.0 unconditionally attaches the kernel touchpad (/dev/input/event7 for HTIX5288:00 0911:5288) as a touchpad source on the default composite device, even on non-Steam-Deck hardware where the user has no Deck-style touchpad rights. This drives libinput into a state where it cannot read the original touchpad and only sees an InputPlumber-generated uinput device.

That breaks KDE Plasma's "Touchpad Settings" page, makes kcminputrc changes silently ignored, and prevents OpenGamepadUI from forwarding any user-tunable parameters (sensitivity, tap-to-click, scroll method, etc.) to Steam Big Picture.

Reproduction steps

1. Boot Bazzite-Deck (44.20260908) on GPD Win Mini 2024 (DMI product_name=G1617-01, sys_vendor=GPD, cpu_vendor=AuthenticAMD).
2. Launch gamescope-session-plus ogui-steam.
3. Run libinput list-devices from a Plasma user session — HTIX5288 touchpad is missing.
4. Inspect InputPlumber over DBus:

$ dbus-send --system --print-reply \
    --dest=org.shadowblip.InputPlumber \
    /org/shadowblip/InputPlumber/CompositeDevice0 \
    org.freedesktop.DBus.Properties.GetAll \
    string:org.shadowblip.Input.CompositeDevice
  SourceDevicePaths:
    /dev/hidraw1
    /dev/hidraw4
    /dev/input/event4
    /dev/input/event17
    /dev/input/event7   <-- HTIX5288 touchpad
  TargetDevices:
    /org/shadowblip/InputPlumber/devices/target/touchpad0
    /org/shadowblip/InputPlumber/devices/target/gamepad0
    /org/shadowblip/InputPlumber/devices/target/mouse0
    /org/shadowblip/InputPlumber/devices/target/keyboard0

The kernel touchpad is held by InputPlumber's default composite device and re-emitted only as the virtual InputPlumber Touchpad uinput device (/devices/virtual/input/inputXX, ABS touchpad). The host libinput (and therefore kcminputrc / Plasma Touchpad settings) cannot read it.

5. Open Steam Big Picture. The touchpad cursor drifts, two-finger scrolling is broken; the only knob that helps is Steam → Settings → Controller → Touchpad → Cursor Sensitivity.

Expected behavior

On non-Steam-Deck hardware (or on any system whose DMI is not Galileo/Jupiter), InputPlumber should either:

• Pass the kernel touchpad through unchanged so that libinput on the host KDE/Wayland session can manage it, OR
• Emit a uinput touchpad device but also keep a libinput-readable passthrough of the original event node, OR
• Honour a config flag (e.g. an ignore_classes: [touchpad] option in default.yaml, or a udev tag like ENV{BAZZITE_TOUCHPAD_PASSTHROUGH}="1").

Suggested fix

In rootfs/usr/share/inputplumber/profiles/default.yaml, the matches: [] is empty — the profile matches every machine. Add either:

1. A DMI allow-list so that the default composite only auto-manages gamepad/keyboard on Steam Deck-style hardware, or
2. A source_device class filter that skips DeviceClass=touchpad unless a Deck-style controller (Valve 28de:1205) is paired, or
3. A new schema field options.ignore_classes: ["touchpad"] so users can opt out per profile.

Workaround today:

# /etc/inputplumber/devices.d/zz-99-touchpad-passthrough.yaml
version: 1
kind: CompositeDevice
name: Local — touchpad passthrough
matches:
  - dmi_data:
      product_name: G1617-01
      sys_vendor: GPD
source_devices:
  - group: gamepad
    udev:
      properties:
        - name: ID_INPUT_JOYSTICK
          value: "1"
      sys_name: "event*"
      subsystem: input
  - group: keyboard
    evdev:
      name: AT Translated Set 2 keyboard
      handler: event*
options:
  auto_manage: true
target_devices:
  - mouse
  - keyboard
  - gamepad

After restarting InputPlumber, manually dbus-send --print-reply --dest=org.shadowblip.InputPlumber /org/shadowblip/InputPlumber/CompositeDevice0 org.shadowblip.Input.CompositeDevice.Stop and add a udev rule tagging the kernel touchpad with TAG+="uaccess" so libinput can finally read it. This is fragile and should not be required.

Environment

• InputPlumber 0.79.0
• Bazzite 44.20260908 (ghcr.io/ublue-os/bazzite-deck:stable)
• Decky Loader 3.2.8
• OpenGamepadUI (current packaged)
• Steam client 1788652215
• Kernel 6.16.x
• Touchpad: HTIX5288:00 0911:5288 (i2c, 67x48 mm, multitouch, USB ID 0911:5288)