Tock Components

Components in Tock are helper files that simplify initializing a board with various capsules and other resources.

Motivation

Initializing a board mainly consists of three steps:

1. Setting any MCU-specific configurations necessary for the MCU to operate correctly.
2. Statically declaring memory for various kernel resources (i.e. capsules) and configuring the capsules correctly.
3. Loading processes, configuring the core kernel, and starting the kernel.

Components are designed to simplify the second step (configuring capsules) while also reducing the chance for misconfiguration or other setup errors.

Configuring capsules can be tricky because i) the exact type needs to be specified, and types can be complicated and tedious to define correctly, ii) capsules can be complex and require several arguments or setup steps, and iii) capsules often require set_client() to be called to setup in-kernel callback chains, and these can be easy to forget. Components allow most of a capsule's configuration to be written just once in a component, and then various boards can use the component to reduce the complexity of their setup code and reduce the chance for errors. Components also reduce the burden when changes are made to capsules, as the change can likely be reflected in the single component and not in every board's main.rs file.

Adding Components

We are always happy to merge new components for various capsules or different configurations. Generally copying an existing component is the best place to start when creating a new component.