# surface-dial-linux

A Linux userspace controller for the [Microsoft Surface Dial](https://www.microsoft.com/en-us/p/surface-dial/925r551sktgn). Requires Linux Kernel 4.19 or higher.

- Uses the [`evdev`](https://en.wikipedia.org/wiki/Evdev) API + `libevdev` to read events from the surface dial.
- Uses `libevdev` to fake input via `/dev/uinput` (for keypresses / media controls)

**DISCLAIMER: This is WIP software!**

Things will change.
Things will break.
Things are probably buggy.

There's also a non-zero chance that I'll just stop working on it at some point once I decide that it's Good Enough:tm: for me.

You've been warned :eyes:

## Overview

Consists of two components:

- `surface-dial-daemon` - A background daemon which recieves raw events and translates them to various actions.
- `surface-dial-cli` - Controller to configure daemon functionality (e.g: change operating modes)

It would be cool to create some sort of GUI overlay (similar to the Windows one), though that's a bit out of scope at the moment.

## Functionality

- [x] Interpret raw Surface Dial event
- [ ] Dynamically switch between operating modes
    - [ ] Context-sensitive (based on currently open application)
    - [ ] Using `surface-dial-cli` application
    - [ ] Using some-sort of on-device mechanism (e.g: long-press)
- Various Operating Modes
    - [x] Volume Controls
    - [x] Media Controls
    - [x] D-Pad (emulated left, right, and space key)
    - [ ] Scrolling / Zooming

Feel free to suggest / contribute new features!

## Building

Building `surface-dial-daemon` requires the following:

- A fairly recent version of the Rust compiler
- `libevdev`

If `libevdev` is not installed, the `evdev_rs` Rust library will try to build it from source, which may require other bits of build tooling. As such, it's recommended to install `libevdev` if it's available through your distribution.

```bash
# e.g: on ubuntu
sudo apt install libevdev-dev
```

Otherwise, `surface-dial-daemon` uses the bog-standard `cargo build` flow.

```bash
cargo build -p surface-dial-daemon --release
```

The resulting binary is output to `target/release/surface-dial-daemon`

## Running `surface-dial-daemon`

For testing changes locally, you'll typically want to run the following:

```bash
cargo build -p surface-dial-daemon && sudo target/debug/surface-dial-daemon
```

Note the use of `sudo`, as `surface-dial-daemon` requires permission to access files under `/dev/input/` and `/dev/uinput`.

## Using `surface-dial-cli`

TODO (the controller cli doesn't exist yet lol)

## Installation

As you might have noticed, the daemon dies whenever the Surface Dial disconnects (which happens after a brief period of inactivity).

I personally haven't figured out a good way to have the daemon gracefully handle the dial connecting/disconnecting (PRs appreciated!), so instead, I've come up with a [cunning plan](https://www.youtube.com/watch?v=AsXKS8Nyu8Q) to spawn the daemon whenever the Surface Dial connects :wink:

This will only work on systems with `systemd`.
If your distro doesn't use `systemd`, you'll have to come up with something yourself I'm afraid...

```bash
# Install the `surface-dial-daemon` (i.e: build it, and place it under ~/.cargo/bin/surface-dial-daemon)
# You could also just copy the executable from /target/release/surface-dial-daemon to wherever you like.
cargo install --path .

# IMPORTANT: modify the .service file to reflect where you placed the `service-dial-daemon` executable
vi surface-dial.service

# install the systemd service
sudo cp surface-dial.service /etc/systemd/system/surface-dial.service
# install the service-dial udev rule
sudo cp surface-dial-udev.rules /etc/udev/rules.d/50-surface-dial.rules

# reload systemd + udev
sudo systemctl daemon-reload
sudo udevadm control --reload
```

You many need to disconnect + reconnect the Surface Dial for the `udev` rule to trigger.

## License

At the moment, this software is deliberately unlicensed. I'm not opposed to adding a license at some point, it's moreso that I don't think the project is at the stage where it needs a license.