This example demonstrates how a client can use the fuchsia.power.SuspendEnabled configuration capability to gate its power-management behavior at runtime. There isn‘t any meaningful power management to be done here; rather, the example demonstrates how to make your way from the configuration capability to an if/else block based on its value, with a test protocol and component to guarantee that all works. In that respect, it’s mostly an example of how to use a configuration capability, but specific to the capability you should use for gating power management behavior.
This example is currently implemented only in Rust. Addition of a C++ version can be prioritized upon request.
The most relevant pieces are summarized below.
The configuration client‘s manifest includes a use declaration for the fuchsia.power.SuspendEnabled capability, indicating that its value should be stored in the should_manage_power field of the client’s structured configuration. You can use a different field name if you would prefer.
The fuchsia_structured_config_rust_lib template uses the client's manifest to generate a library for its structured configuration.
The ConfigUser protocol provides a way for the configuration client to expose whether it is managing power. The protocol is contrived for this example - it just provides a way for the client to change some behavior in a way that is observable to the test component.
The client reads its structured configuration. It uses the value of should_manage_power to determine what value it will return to a caller oftest.configexample/ConfigUser.IsPowerManaged.
The test component implements the fuchsia.power.SuspendEnabled capability with a value determined by each test case. It routes this capability to the client, then queries the client via ConfigUser.IsPowerManaged to verify that the client is using the appropriate value of this capability.