Crate videocore_gencmd

Provides actual bindings and wrapper around VideoCore gencmd interface.

The raw bindings are available in the ffi module.

Currently implemented commands can be seen in gencmd::commands module. Note that since the gencmd interface is a simple textual protocol it can be used even without an explicit implementation (see Gencmd::send_cmd_raw). The advantage of implementing a command specifically is parsing of the response into an appropriate type.

Usage

There are two patterns this library supports out of the box:

Unique instance

The GencmdUnique convenience wrapper provides an easy way to create a unique instance to be used on one thread at a time.

Note that there can ever only be one instance of the global context per-process. Attempting to create multiple instances returns an error. If you need access from multiple threads simultaneously consider using the global singleton or implementing a similar solution yourself.

use videocore_gencmd::prelude::*;
fn main() -> Result<(), Box<dyn std::error::Error>> {
	let mut gencmd = GencmdUnique::new()?;

	let temperature = gencmd.send_cmd::<CmdMeasureTemp>()?;

	println!("VC temperature is: {}", temperature);

	Ok(())
}

Global multi-threaded instance

The unique instance approach should be sufficient for most usecases. However, sometimes it is required to invoke gencmd interface from multiple threads at one time. For this there is the global_singleton feature that exposes a global, lazy-initialized, weak-pointed singleton and a convenience GencmdGlobal.

use videocore_gencmd::prelude::*;
fn main() {
	let temperature_measurer =
		std::thread::spawn(|| -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
			let mut gencmd = GencmdGlobal::new()?;

			let mut limit = 3;
			while limit > 0 {
				let temperature = gencmd.send_cmd::<CmdMeasureTemp>()?;
				println!("VC temperature is: {}", temperature);

				std::thread::sleep(std::time::Duration::from_secs(1));
				limit -= 1;
			}

			Ok(())
		});

	let freq_measurer =
		std::thread::spawn(|| -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
			let mut gencmd = GencmdGlobal::new()?;

			let mut limit = 3;
			while limit > 0 {
				let frequency = gencmd.send_cmd::<CmdMeasureClockArm>()?;
				println!("Arm frequency is: {} Hz", frequency);

				std::thread::sleep(std::time::Duration::from_secs(1));
				limit -= 1;
			}

			Ok(())
		});

	temperature_measurer.join().unwrap();
	freq_measurer.join().unwrap();
}

Features

run_bindgen

Runs the bindgen in build.rs. Without this feature enabled the bindings previously generated and pasted into the sources are used instead as the bindgen cannot be used on all platforms.

mock_vc_ffi

FFI bindings naturally expect a library to link against. For testing purposes this is not always ideal, so this feature instead exposes C ABI functions that match the bindings and mock the interface to some extent.

cli_app

This feature gates optional crates needed to build the cli app which functionally mirrors the C binary vcgencmd.

global_singleton

Enables the global singleton implementation as described above.

Modules

error

ffi

gencmd

global

prelude