gpiosim

A Go library for creating and controlling GPIO simulators for testing users of the Linux GPIO uAPI (both v1 and v2).

The simulators are provided by the Linux gpio-sim kernel module and so require a recent kernel (5.19 or later) built with CONFIG_GPIO_SIM.

Simulators contain one or more Chips, each with a collection of lines being simulated. Configuring a simulator involves adding Banks, eash representing a chip, to NewSim, which will construct the corresponding simulator using gpio-sim and take it live.

Once live, the Chip exposes lines which may be manipulated to drive the GPIO uAPI from the kernel side. For input lines, applying a pull using Chip pull methods controls the level of the simulated line. For output lines, the Chip.Level method returns the level the simulated line is being driven to by userspace.

For tests that only require vanilla lines on a single chip, the Simpleton provides a slightly simpler interface.

Closing the Sim deconstructs the simulator, removing the gpio-sim configuration and the corresponding gpiochips.

Configuring a simulator involves configfs, and manipulating the chips once live involves sysfs, so root permissions are typically required to run a simulator.

Example Usage

Creating a simulator with two chips, with 8 and 42 lines respectively, each with several named lines and some hogged lines:

s, err := gpiosim.NewSim(
	gpiosim.WithName("gpiosim_test"),
	gpiosim.WithBank(gpiosim.NewBank("left", 8,
		gpiosim.WithNamedLine(3, "LED0"),
		gpiosim.WithNamedLine(5, "BUTTON1"),
		gpiosim.WithHoggedLine(2, "piggy", gpiosim.HogDirectionOutputLow),
	)),
	gpiosim.WithBank(gpiosim.NewBank("right", 42,
		gpiosim.WithNamedLine(3, "BUTTON2"),
		gpiosim.WithNamedLine(4, "LED2"),
		gpiosim.WithHoggedLine(7, "hogster", gpiosim.HogDirectionOutputHigh),
		gpiosim.WithHoggedLine(9, "piggy", gpiosim.HogDirectionInput),
	)),
)
defer s.Close()
c := &sim.Chips[0]
c.Pullup(5);
level, err := c.Level(3);

Use a Simpleton to create a single chip simulator with 12 lines, for where multiple chips or named lines are not required:

s, err := gpiosim.NewSimpleton(12)
s.SetPull(5, 1)
level, err := s.Level(3)

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.