# galahad2lcd

A modern Go driver for the **Lian Li Galahad II LCD** cooler display. It
transcodes a video or GIF to H.264 and streams it over USB to the 480×480
LCD, running as a systemd service.

This is a clean-room rewrite of the archived
[GalahadII_LCD_Linux](https://github.com/H4rk3nz0/GalahadII_LCD_Linux)
project. It keeps the exact wire protocol but drops the fragile FFmpeg C-ABI
dependency in favour of the system `ffmpeg` binary, adds structured logging,
automatic USB reconnection and a testable, layered architecture.

## Features

- `daemon` — transcodes media to H.264 and streams it in a loop
- `set` — change the input/rotation/speed and restart the service
- `list` — enumerate USB devices to diagnose connectivity
- `version` — print the build version
- Automatic reconnect if the USB link is lost (e.g. after suspend)
- Graceful shutdown on SIGINT/SIGTERM (`systemctl stop` works cleanly)
- Structured logs (`log/slog`) captured by journald
- Rotation, playback speed and framerate overrides via config or flags

## Requirements

- Go 1.22+ (to build)
- FFmpeg + FFprobe (any recent version, e.g. `sudo pacman -S ffmpeg`)
- libusb (transitive build dependency of `github.com/google/gousb`)
- systemd

## Install

```sh
sudo ./packaging/install.sh /path/to/media.gif
```

The script builds the binary, installs the systemd unit and udev rule, writes
an initial config and starts the service. If no media file is given, configure
it afterwards:

```sh
sudo galahad2lcd set --input /path/to/media.gif --rotate 0
```

## Configuration

Settings live in `/etc/galahad2lcd.toml`:

```toml
[display]
input = "/home/user/media.gif"
rotate = 0        # 0, 90, 180, 270 (clockwise)
speed = 1.0       # >1 slower, <1 faster

[usb]
vendor_id = 0x0416
product_id = 0x7395

[stream]
fps = 0           # 0 = auto-detect from the source
cache_path = "/tmp/galahad_cache.h264"
```

The `set` command updates this file and restarts the service:

```sh
sudo galahad2lcd set --input /home/user/media.gif --rotate 90 --speed 1.2
sudo galahad2lcd set --fps 15 --no-restart   # apply later
```

CLI flags also override the config for one-off runs:

```sh
sudo galahad2lcd daemon --input /home/user/media.gif --rotate 180
```

## Diagnostics

```sh
galahad2lcd list                # find the LCD on the USB bus (needs udev rule or root)
journalctl -u galahad2lcd -f    # live daemon logs
```

The bundled udev rule (`packaging/99-galahad2lcd.rules`) grants the
logged-in session user access to the device so `list` works without root.

## Architecture

```
cmd/galahad2lcd      entry point (composition root)
internal/cli         cobra commands: daemon, set, list, version
internal/config      TOML configuration model, load/save/validate
internal/transcoder  ffmpeg/ffprobe wrapper, filter graph, FPS detection
internal/h264        Annex-B stream → access-unit splitting (pure Go)
internal/stream      frame-rate pacing loop (testable, device-agnostic)
internal/device      Device interface + gousb (libusb) implementation
internal/protocol    USB framing (pure functions, golden-tested)
internal/service     systemd unit management
```

Layers depend only downward. `stream` talks to a `device.Device` interface,
so the transport can be swapped or faked in tests without touching the rest
of the pipeline.

## Development

```sh
make build     # build ./bin/galahad2lcd
make test      # unit + integration tests (integration needs ffmpeg)
make vet       # go vet
make fmt       # gofmt
make install   # copy binary to /usr/local/bin
```

## Uninstall

```sh
sudo ./packaging/uninstall.sh
```

## License

MIT