usb-gadget

This library allows implementation of USB peripherals, so called USB gadgets, on Linux devices that have a USB device controller (UDC). Both, pre-defined USB functions and fully custom implementations of the USB interface are supported.

The following pre-defined USB functions, implemented by kernel drivers, are available:

• network interface
  • CDC ECM
  • CDC ECM (subset)
  • CDC EEM
  • CDC NCM
  • RNDIS
• serial port
  • CDC ACM
  • generic
• human interface device (HID)
• mass-storage device (MSD)
• printer device
• musical instrument digital interface (MIDI)
• audio device (UAC1 and UAC2)
• video device (UVC)

In addition fully custom USB functions can be implemented in user-mode Rust code.

Support for OS-specific descriptors and WebUSB is also provided.

CLI tool

The usb-gadget CLI tool allows you to configure USB gadgets from TOML configuration files without writing any Rust code.

Installation

cargo install usb-gadget --features cli

Usage

Create a TOML configuration file describing your gadget, then use the CLI to manage it:

usb-gadget up gadget.toml       # register and bind a gadget
usb-gadget list                 # list registered gadgets
usb-gadget down my-gadget       # remove a gadget by name
usb-gadget down --all           # remove all gadgets
usb-gadget check gadget.toml    # validate a config file

You can also pass a directory to up or check to process all .toml files in it.

Example configuration

name = "serial-debug"

[device]
vendor = 0x1209
product = 0x0002
manufacturer = "Example Inc."
product_name = "Debug Console"
serial = "0001"

[[config]]
description = "Serial Config"

[[config.function]]
type = "serial"
class = "acm"

Multiple functions can be combined in a single gadget by adding more [[config.function]] entries. Run usb-gadget template --list to see all available templates.

Features

This crate provides the following optional features:

• cli: builds the usb-gadget CLI tool for configuring gadgets from TOML files.
• tokio: enables async support for custom USB functions on top of the Tokio runtime.

Requirements

The minimum supported Rust version (MSRV) is 1.77.

A USB device controller (UDC) supported by Linux is required. Normally, standard PCs do not include an UDC. A Raspberry Pi 4 contains an UDC, which is connected to its USB-C port.

The following Linux kernel configuration options should be enabled for full functionality:

• CONFIG_USB_GADGET
• CONFIG_USB_CONFIGFS
• CONFIG_USB_CONFIGFS_SERIAL
• CONFIG_USB_CONFIGFS_ACM
• CONFIG_USB_CONFIGFS_NCM
• CONFIG_USB_CONFIGFS_ECM
• CONFIG_USB_CONFIGFS_ECM_SUBSET
• CONFIG_USB_CONFIGFS_RNDIS
• CONFIG_USB_CONFIGFS_EEM
• CONFIG_USB_CONFIGFS_MASS_STORAGE
• CONFIG_USB_CONFIGFS_F_FS
• CONFIG_USB_CONFIGFS_F_HID
• CONFIG_USB_CONFIGFS_F_PRINTER
• CONFIG_USB_CONFIGFS_F_MIDI
• CONFIG_USB_CONFIGFS_F_UAC1
• CONFIG_USB_CONFIGFS_F_UAC2
• CONFIG_USB_CONFIGFS_F_UVC

root permissions are required to configure USB gadgets on Linux and the configfs filesystem needs to be mounted.

License

usb-gadget is licensed under the Apache 2.0 license.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in usb-gadget by you, shall be licensed as Apache 2.0, without any additional terms or conditions.