USB-WASM

Prototype design and implementation of an interface for accessing and communicating with USB devices from a WebAssembly Component. This project forms part of my Master's thesis.

Repository structure

• ./wit/ contains the interface definition in the WIT IDL.
• ./usb-wasm contains the host implementation of the interface for Wasmtime.
• ./usb-wasm-bindings contains the automatically generated Rust bindings. This crate is used in the example/test command components.
• ./command-components contains a couple of command components implemented using the interface.
• ./wasmtime-usb implements a Component Model-enabled Wasmtime CLI application to run command components that use the interface.

Requirements

• Rust
• wasm-tools
• just

Building

We use just as build system. You can see all supported commands by running just --list. You can build the modified wasmtime runtime with the following command.

just build-runtime

You can also use just to build any of the guest components (command components). For example, to build the xbox pacman demo, run the following.

just build-xbox-maze

Afterwards, you can run this demo using the following command.

sudo ./target/debug/wasmtime-usb out/xbox-maze.wasm

Building components manually

Instead of using just, you can also build the components manually using the following method.

Because Rust can only target WASI preview 1 right now, the compiled WASM binaries first need to be transformed into command components before they can be run by the Component Model-enabled Wasmtime CLI.

wasm-tools is used to 'adapt' the WASM binaries compiled by rustc into command components.

For example, to run the lsusb command component, the following commands have to be executed:

> cargo build -p lsusb --target=wasm32-wasi 
> wasm-tools component new ./target/wasm32-wasi/debug/lsusb.wasm --adapt ./command-components/wasi_snapshot_preview1.command.wasm -o out/lsusb.wasm
> cargo run -- ./out/lsusb.wasm

If you have the just command runner installed, you can just run just lsusb, which will perform all these steps for you.

Best xbox pacman performance

Since the game uses CLI output, it needs to write this line per line. This might cause some flickering. For best performance, use Alacritty with a font size of 30 and in fullscreen.

Funding information

This work has been partially supported by the ELASTIC project, which received funding from the Smart Networks and Services Joint Undertaking (SNS JU) under the European Union’s Horizon Europe research and innovation programme under Grant Agreement No 101139067. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.