Overview

This directory contains testing utilities for working with a CFv2-compatible Isolated DevMgr component.

Usage

There are two main ways to use the CFv2 IsolatedDevMgr:

1. Define an isolated_devmgr_v2_component component locally, which exposes a /dev directory. With this GN template, the client is responsible for routing the /dev dir into their test component's namespace as necessary. This would generally be via CML, but could also be done at runtime in Rust via the fuchsia_component_test::RealmBuilder.
2. Define an isolated_devmgr_unittest_v2_component component to be a child component of the test component, ensuring it is packaged alongside the test component. Then, one uses either the C++ OneTimeSetup or Rust launch_isolated_driver_manager utility to bind the isolated driver manager‘s /dev directory into the test component’s namespace dynamically.

Internals

We'll examine the GN targets in this directory to get a better sense of how they fit together:

Core library elements:

• “:driver-manager-test” GN target: Contains the production Driver Manager/Driver Host binaries, i.e. the underlying driver management logic. This component runs the binaries with capabilities from its parent - so this makes the device manager isolatable, but does not actually provide the capabilities which make the device manager “isolated”.
• “:support” GN target: The device manager binaries require access to the kernel/RootJob and boot/Arguments capabilities, so this helper binary provides a fake implementation of these services for the IsolatedDevMgr.

Client utilities:

• isolated_devmgr.gni: This GNI file defines two templates, both of which are mentioned in Usage. The first, isolated_devmgr_v2_component, takes only a package name. It defines an IsolatedDevMgr component that exposes a directory capability named dev in that package. The second, isolated_devmgr_unittest_v2_component, takes a test executable and package name as input and generates a unit test component with a child IsolatedDevMgr component. Tests that use this template generally use one of the following client libraries.
• “:client” GN target: This source_set provides C++ utility functions for the IsolatedDevMgr. The bind_devfs_to_namespace header can be used to set up a test component's /dev directory with the isolated devfs exposed by a child IsolatedDevMgr.
• “rust:isolated-driver-manager” GN target: Similar to the C++ client target, this provides Rust library functions for working with an existing child IsolatedDevMgr component, including a helper to bind the child IsolatedDevMgr's /dev directory to the test component.