gpio.hpp

#pragma once

#include <linux/gpio.h>
#include "file.hpp"

namespace witherspoon
{
namespace gpio
{

typedef std::remove_reference<decltype(
     gpiohandle_request::lineoffsets[0])>::type gpioNum_t;

typedef std::remove_reference<decltype(
     gpiohandle_data::values[0])>::type gpioValue_t;

/**
 * If the GPIO is an input or output
 */
enum class Direction
{
    input,
    output
};

/**
 * The possible values - low or high
 */
enum class Value
{
    low,
    high
};

/**
 * Represents a GPIO.
 *
 * Currently supports reading a GPIO.
 *
 * Write support may be added in the future.
 */
class GPIO
{
    public:

        GPIO() = delete;
        GPIO(const GPIO&) = delete;
        GPIO(GPIO&&) = default;
        GPIO& operator=(const GPIO&) = delete;
        GPIO& operator=(GPIO&&) = default;
        ~GPIO() = default;

        /**
         * Constructor
         *
         * @param[in] device - the GPIO device file
         * @param[in] gpio - the GPIO number
         * @param[in] direction - the GPIO direction
         */
        GPIO(const std::string& device,
             gpioNum_t gpio,
             Direction direction) :
            device(device),
            gpio(gpio),
            direction(direction)
        {
        }

        /**
         * Reads the GPIO value
         *
         * Requests the GPIO line if it hasn't been done already.
         *
         * @return Value - the GPIO value
         */
        Value read();

        /**
         * Sets the GPIO value to low or high
         *
         * Requests the GPIO line if it hasn't been done already.
         *
         * @param[in] Value - the value to set
         */
        void set(Value value);

    private:

        /**
         * Requests a GPIO line from the GPIO device
         *
         * @param[in] defaultValue - The default value, required for
         *                           output GPIOs only.
         */
        void requestLine(Value defaultValue = Value::high);

        /**
         * The GPIO device name, like /dev/gpiochip0
         */
        const std::string device;

        /**
         * The GPIO number
         */
        const gpioNum_t gpio;

        /**
         * The GPIO direction
         */
        const Direction direction;

        /**
         * File descriptor for the GPIO line
         */
        power::util::FileDescriptor lineFD;
};

}
}