Docs / Getting Started

Getting Started

Five minutes to a working device driver -- just copy, paste, run

This page gets you to a running driver in five minutes. Copy the code, run it, see it work. For a detailed walkthrough that explains every decision, see Build Your First Driver.

What you’ll build

A bidirectional echo device at /dev/echo. Write bytes in, read them back. Fifteen lines of driver logic.

Shell:
  exec 3<>/dev/echo
  echo hello >&3
  cat <&3              # prints "hello"
  exec 3>&-

Prerequisites

  • Dart SDK 3.0 or later
  • A BentOS machine (or any Unix for local testing)

The Dart binding is the reference implementation. Python, Rust, Go, and JavaScript bindings will follow the same patterns and ops contracts described in these docs.

1. Create a new project

mkdir echo-driver && cd echo-driver
dart create -t console .

Add the SDK dependency to your pubspec.yaml:

dependencies:
  bentos_driver_sdk:
    git:
      url: https://github.com/anthropics/bentos-driver-sdk-dart.git

Then fetch:

dart pub get

2. Write the driver

Replace bin/echo_driver.dart with:

import 'dart:async';
import 'dart:typed_data';

import 'package:bentos_driver_sdk/bentos_driver_sdk.dart';

void main() async {
  final driver = StreamDriver<StreamController<Uint8List>>(StreamOps(
    onSessionStart: (flags) => StreamController<Uint8List>(),
    onData: (data, {required session}) {
      session!.add(Uint8List.fromList(data));
      return data.length;
    },
    outputStream: ({required session}) => session!.stream,
    onSessionEnd: ({required session}) => session!.close(),
  ));

  await driver.serve(Uri.parse('unix:///tmp/bentos-echo.sock'));
  print('Echo driver listening. Ctrl-C to stop.');

  await ProcessSignal.sigint.watch().first;
  await driver.close();
}

That’s it. Four callbacks, no FUSE vocabulary, no protobuf. Just domain logic.

3. Run it

dart run bin/echo_driver.dart

The driver is now listening on a Unix socket. On a BentOS machine, bentosd connects to this socket and exposes it as /dev/echo. For local testing, you can use the SDK’s test utilities or connect directly.

What just happened

You wrote a device driver. You implemented four domain callbacks (the “ops contract”), and the SDK handled everything else: the wire protocol, session management, poll readiness, error translation.

The SDK has four I/O patterns like this one. Each gives you a different relationship between reads and writes. The echo driver uses Pattern 1 (Pure Stream) – bidirectional, independent streams.

Next steps