Support systemd notifications

[RWebster-Noble]

Fixes an issue where systemd would incorrectly detect the service as hung, causing restart loops.
Also updated code to allow the service to be shutdown cleanly.

Changes

Event Loop Management

• Replaced manual event loop handling with asyncio.run() for cleaner shutdown and automatic cleanup

Systemd Integration

• Added Type=notify to the service file to support service state tracking
• Implemented sd-notify for systemd ready-state signaling
• Added graceful shutdown handlers for SIGTERM/SIGINT signals to ensure clean termination
• Added some informational logs

Service

• Updated service example to use notify type

Dependencies

• Added sd-notify = "^0.1.0"

[BryanJacobs]

This looks clean, but I think it has a bug: because systemd is not a dependency of the Python package, there's no guarantee it's installed. That's fine because you've added a dynamic import guard.

But the systemd unit is changed to use notify as the startup type. The notification will never be received if the sd_notify package isn't installed. The service will be stuck in the starting state.

Your description of the PR says you've added sd-notify as a dependency but you have not.

[RWebster-Noble]

Your description of the PR says you've added sd-notify as a dependency but you have not.

Opps, got a bit overzealous with my tidying up.

I've added that now.

I also realised that doing a optional import is a bit redundant with this being a dependency so I just made that a regular import.

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I decided to do a test by installing this on a fresh Ubuntu 24.04 VM and got this error:

c/_cffi_backend.c:6112:9: error: implicit declaration of function '_PyErr_WriteUnraisableMsg'; did you mean 'PyErr_WriteUnraisable'? [-Wimplicit-function-declaration]

So to fix that I added an updated dependency for cffi ^1.17.0 for Python 3.14 compatibility.

Here's my full test after fixing that:

sudo apt-get update
sudo apt-get install -y pipx gcc libffi-dev libpcsclite-dev swig python3-dev pcscd

pipx ensurepath
export PATH=$HOME/.local/bin:$PATH
pipx install poetry

cd fido2-hid-bridge/

poetry install

sudo mkdir -p /opt/fido2-hid-bridge
sudo cp -r . /opt/fido2-hid-bridge/
sudo cp fido2-hid-bridge.service /etc/systemd/system/
cd /opt/fido2-hid-bridge && sudo -E $HOME/.local/bin/poetry install

sudo systemctl daemon-reload
sudo systemctl enable --now fido2-hid-bridge

Test stop and start:

$ sudo systemctl status fido2-hid-bridge.service

● fido2-hid-bridge.service - Fido2 to HID bridge
     Loaded: loaded (/etc/systemd/system/fido2-hid-bridge.service; enabled; preset: enabled)
     Active: active (running) since Sun 2026-03-08 11:26:09 UTC; 1min 20s ago
   Main PID: 710 (fido2-hid-bridg)
      Tasks: 1 (limit: 4601)
     Memory: 31.1M (peak: 31.4M)
        CPU: 129ms
     CGroup: /system.slice/fido2-hid-bridge.service
             └─710 /opt/fido2-hid-bridge/.venv/bin/python /opt/fido2-hid-bridge/.venv/bin/fido2-hid-bridge

Mar 08 11:26:08 systemd[1]: Starting fido2-hid-bridge.service - Fido2 to HID bridge...
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:UHIDDevice:initializing device
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:UHIDDevice:(UHID_CREATE2) create UHIDDevice(vid=39321, pid=39321, name=FIDO2 Virtual USB Device, uniq=UHIDDevice_b586f6c9-fffa-4721-a2b6-cee42be0f15a)
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:root:FIDO2 HID Bridge started successfully
Mar 08 11:26:09 systemd[1]: Started fido2-hid-bridge.service - Fido2 to HID bridge.

$ sudo systemctl stop fido2-hid-bridge.service

$ sudo systemctl status fido2-hid-bridge.service --no-pager 
○ fido2-hid-bridge.service - Fido2 to HID bridge
     Loaded: loaded (/etc/systemd/system/fido2-hid-bridge.service; enabled; preset: enabled)
     Active: inactive (dead) since Sun 2026-03-08 11:27:43 UTC; 2s ago
   Duration: 1min 34.129s
    Process: 710 ExecStart=/opt/fido2-hid-bridge/.venv/bin/fido2-hid-bridge (code=exited, status=0/SUCCESS)
   Main PID: 710 (code=exited, status=0/SUCCESS)
        CPU: 138ms

Mar 08 11:26:08 systemd[1]: Starting fido2-hid-bridge.service - Fido2 to HID bridge...
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:UHIDDevice:initializing device
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:UHIDDevice:(UHID_CREATE2) create UHIDDevice(vid=39321, pid=39321, name=FIDO2 Virtual USB Device, uniq=UHIDDevice_b586f6c9-fffa-4721-a2b6-cee42be0f15a)
Mar 08 11:26:09 fido2-hid-bridge[710]: INFO:root:FIDO2 HID Bridge started successfully
Mar 08 11:26:09 systemd[1]: Started fido2-hid-bridge.service - Fido2 to HID bridge.
Mar 08 11:27:43 systemd[1]: Stopping fido2-hid-bridge.service - Fido2 to HID bridge...
Mar 08 11:27:43 fido2-hid-bridge[710]: INFO:root:Received signal SIGTERM, shutting down...
Mar 08 11:27:43 fido2-hid-bridge[710]: INFO:root:FIDO2 HID Bridge shutting down...
Mar 08 11:27:43 systemd[1]: fido2-hid-bridge.service: Deactivated successfully.
Mar 08 11:27:43 systemd[1]: Stopped fido2-hid-bridge.service - Fido2 to HID bridge.

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I also set PYTHONUNBUFFERED per the advice here.