surface-dial-linux/README.md

# 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)
- Uses `hidapi` to configure dial sensitivity + haptics

**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

`surface-dial-daemon` is a background daemon which recieves raw events and translates them to various actions.

Aside from haptic feedback, the daemon also uses FreeDesktop notifications to provide visual feedback when performing various actions.

![](notif-demo.gif)

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

## Functionality

- [x] Interpret raw Surface Dial event
- Operating Modes
    - [x] Volume Controls
    - [x] Media Controls
    - [x] D-Pad (emulated left, right, and space key)
    - [x] Scrolling / Zooming
    - [ ] \(meta\) custom modes specified via config file(s)
- [x] Dynamically switch between operating modes
    - [x] Using some-sort of on-device mechanism (e.g: long-press)
    - [ ] Context-sensitive (based on currently open application)
- [ ] Mode Persistence
    - _At the moment, whenever the dial disconnects, the daemon is re-launched, which resets the active mode to the default one. It would be good to have some on-disk persistence to remember the last selected mode._
- [x] Haptic Feedback
    - https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/radial-controller-protocol-implementation
    - https://www.usb.org/sites/default/files/hutrr63b_-_haptics_page_redline_0.pdf
    - https://www.usb.org/sites/default/files/hut1_21.pdf
    - _This was tricky to figure out, but in the end, it was surprisingly straightforward! Big thanks to [Geo](https://www.linkedin.com/in/geo-palakunnel-57718245/) for pointing me in the right direction!_
- [x] Desktop Notifications
    - [x] On Launch
    - [x] When switching between modes
    - [x] When switching between sub-modes (e.g: scroll/zoom)

Feel free to contribute new features!

## Dependencies

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

- Linux Kernel 4.19 or higher
- A fairly recent version of the Rust compiler
- `libevdev`
- `hidapi`

You can install Rust through [`rustup`](https://rustup.rs/).

Unless you're a cool hackerman, the easiest way to get `libevdev` and `hidapi` is via your distro's package manager.

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

## Building

`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`.

## 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 ./install/surface-dial.service

# create new group for uinput
# (the 99-uinput.rules file changes the group of /dev/uinput to this new group)
sudo groupdadd -f uinput

# add self to the new uinput group and the existing /dev/input group
sudo gpasswd -a $(whoami) uinput
sudo gpasswd -a $(whoami) $(stat -c "%G" /dev/input/event0)

# install the systemd user service
mkdir -p ~/.config/systemd/user/
cp ./install/surface-dial.service ~/.config/systemd/user/surface-dial.service

# install the udev rules
sudo cp ./install/99-uinput.rules /etc/udev/rules.d/99-uinput.rules
sudo cp ./install/50-surface-dial.rules /etc/udev/rules.d/50-surface-dial.rules

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

You may need to reboot to have the various groups / udev rules propagate.

## 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.