libinput-rs

libinput-rs is a 100% drop-in replacement for libinput 1.31.3 on x86_64 Ubuntu, DNF/RPM, and Arch-based systems. It implements the libinput.so.10 C ABI and ships the matching runtime, development, command-line, udev, and quirks package surface.

Release 0.3.3 is validated against upstream libinput 1.31.3 commit 26191d396d74d505541d6311f0b4ae68d791b890. The release gate covers all 309 public symbols, 25 symbol-version nodes, SONAME libinput.so.10, and all 23,245 pinned behavioral cases. The verified result is 12,185 passes, 11,059 tests that require an upstream-private configuration interface and are therefore not applicable to a public-ABI replacement, one upstream release build skip, and zero failures. The skipped test exercises internal event debugging that upstream explicitly disables in release builds.

Supported systems

Supported package paths are the Corinth PPA for Ubuntu 26.04, COPR for DNF/RPM systems, and the Sisyphus repository for Arch-based distributions. Each path replaces the distribution libinput packages and installs the same shared-library ABI, tools, headers, udev rules, and quirks tree.

Agda and Idris 2 proofs are verified in CI and are not runtime dependencies. GNU Fortran compiles the capability bitmap kernel during the package build; the packaged library therefore depends on the standard libgfortran runtime.

Install on Ubuntu

Published Resolute builds are available from the Corinth PPA:

sudo add-apt-repository ppa:sisyphusaeolides/corinth
sudo apt update
sudo apt install libinput-rs

The source produces Ubuntu's native libinput10, libinput-bin, libinput-dev, and libinput-tools package identities. Installing libinput-rs upgrades those packages together, so existing reverse dependencies continue to resolve without package substitutions.

To build the Debian packages locally:

sudo apt install build-essential cargo rustc debhelper devscripts gfortran \
  meson ninja-build pkgconf libevdev-dev libmtdev-dev libudev-dev \
  libwacom-dev libgtk-3-dev libcairo2-dev libwayland-dev \
  wayland-protocols python3-libevdev python3-pyudev python3-yaml
make check
make test
make deb

To create a signed, offline-buildable Launchpad source upload:

make ppa-source
dput ppa:sisyphusaeolides/corinth \
  ../libinput-rs_0.3.3-1~ppa1~ubuntu26.04.1_source.changes

Install on DNF/RPM systems

sudo dnf copr enable sisyphuscode/libinput-rs
sudo dnf install libinput-rs
systemctl enable --now libinput-rs-elan-resume.service

Install from the Sisyphus repository

Add the repository to /etc/pacman.conf:

[sisyphus]
SigLevel = Optional TrustAll
Server = https://sisyphusaeolides.github.io/Sisyphus-Repo/$arch

Then install it:

sudo pacman -Syy
sudo pacman -S libinput-rs

The package replaces libinput and does not run a resident companion service. Resolution-aware motion, scrolling, tapping, click mapping, and disable-while-typing run in the shared backend used by the compositor. This avoids a second process exclusively grabbing a mixed-capability device and prevents two independent input state machines from competing.

To restore the distribution's original runtime package:

sudo pacman -S libinput

Build on Arch

sudo pacman -S --needed base-devel rust cargo gcc-fortran meson ninja patch \
  libevdev mtdev systemd pkgconf python-libevdev python-pyudev python-yaml \
  curl rpm-tools
make all
make check
make test

The command-line tools are built under target/release/. The ABI library is built at target/release/libinput.so.

Elantech transport recovery

Elantech v4 controllers may expose a touchpad through PS/2 and SMBus. Keep the kernel's automatic transport selection unless the journal specifically shows a failed SMBus handoff. On a machine where SMBus probing itself is the failure, the PS/2 path can be forced with:

sudoedit /etc/default/grub
# Add psmouse.elantech_smbus=0 to GRUB_CMDLINE_LINUX_DEFAULT, then run:
sudo grub-mkconfig -o /boot/grub/grub.cfg
sudo reboot

Confirm the workaround after reboot with cat /sys/module/psmouse/parameters/elantech_smbus; it should print 0.

ThinkPad P53 systems exposing the affected LEN0408 Elantech v4 controller should not force SMBus off. The Arch package installs a narrowly matched udev rule that keeps the PS/2 driver's packet CRC validation enabled as a fallback across boot and hotplug. This rejects corrupted combined TrackPoint, button, and touchpad packets before they reach userspace.

The P53's I2C controller can also remain enumerated while silently ceasing to deliver kernel events. sudo libinput elan-recover safely discovers only devices already bound to elan_i2c, unbinds and rebinds each controller, and waits for its evdev nodes to return. The Arch package enables a non-resident systemd sleep unit that runs this recovery after resume only when DMI identifies a ThinkPad P53. It does not open or grab input devices and exits immediately.

The shared backend normalizes touchpad movement with the kernel-reported axis resolution while preserving libinput's separate accelerated and unaccelerated coordinate channels. Runtime settings use the standard libinput configuration API, so existing compositor and desktop preferences continue to apply.

Replacement layout

The Arch package installs libinput.so.10 in the system linker path together with libinput.h, the unversioned linker name, libinput.pc, and the libinput udev callouts and rules.

The udev backend enumerates /dev/input/event* by directory entry and delegates the first device open to the compositor's open_restricted callback. This keeps startup discovery compatible with logind-managed permissions where the compositor can list device nodes but cannot open them directly.

Discovery is fused in src/hwdetect.rs: a raw post-udev netlink socket, inotify, periodic reconciliation, and direct reads of the udev property database identify candidates without opening them. After restricted-open succeeds, ioctl capabilities and sysfs bitmap fallbacks are combined by the Fortran capforge kernel. Rust and Fortran share classifier regression vectors. src/evtrans.rs centralizes mixed KEY/BTN routing, per-code seat counts, and exactly-once button transitions while libevdev retains packet framing and SYN_DROPPED recovery.

Quirk and hardware-profile resolution

Each context loads one lexically ordered snapshot of the installed quirks tree. A device probe contains its kernel identity and raw udev roles. Matching sections produce one immutable applied-quirks object; AttrEventCode and AttrInputProp mutations then feed the only runtime classifier. The resulting object is retained by the tracked device and seeds motion, click, palm, thumb, tablet, switch, and integration behavior before DEVICE_ADDED is queued. Unknown required fields fail the parity gate. A local AttrDeviceClass hint is accepted only when the kernel capability lattice supports that class, so a profile cannot fabricate input capabilities.

The chwd-style inspection tool shows the deterministic hardware profile plan:

libinput-rs-chwd --auto
libinput-rs-chwd --list-profiles
libinput-rs-chwd --identify /dev/input/event6

Hard DMI, identity, udev, and capability predicates take precedence. The Fortran k-nearest-neighbor and tiny-MLP scorers rank equally eligible profiles and may label an otherwise unmatched device only when their result agrees with the deterministic capability class. Statistical scoring never adds a kernel capability or overrides a hard profile.

Formal safety models

The fail-open and restricted-discovery state machines are modeled three ways under proofs/:

• Agda proves that a grab cannot be authorized while the output sink is absent and that listed event nodes remain discoverable without direct-open access, while also proving balanced physical-button transitions;
• Idris 2 uses indexed states and total transitions so invalid runtime and restricted-open states are unconstructable;
• Fortran provides independently compiled executable reference models for fail-open grabbing, permission-independent discovery, exactly-once descriptor closure, udev-only hotplug, and balanced physical-button lifecycles.

HwDetect.agda additionally proves the device lifecycle and capability-lattice join laws. HwSpec.idr makes hardware classification total and keeps ignored or unclassifiable devices out of the live registry by type.

On Arch, install the formal verification toolchains when needed:

sudo pacman -S --needed agda idris2 gcc-fortran
make proofs

make proofs-strict requires all three compilers and runs every model.

Publishing

The Arch package and crates.io release procedure is documented in RELEASING.md. Crates.io publishes one libinput-rs source crate; system replacement installations should use the Sisyphus package.

Reference behavior

The replacement is pinned to upstream libinput 1.31.3 and tested through its public C ABI. The Arch package also builds and installs the upstream 1.31.3 utility, manual-page, completion, udev-callout, and quirks payload alongside the Rust runtime and development files. make packaging-check and the package build verify the installed payload, loader resolution, dependencies, hardening, and an external C consumer before publication.

License

MIT