#include <linux/init.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/gpio/consumer.h>

// gpiochip0: GPIOs 512-565, parent: platform/3f200000.gpio, pinctrl-bcm2835
// From /sys/kernel/debug/gpio
#define RPI3_BCM2835_GPIO_OFFSET 512
#define BCM_TO_LINUX_GPIO(bcm) (RPI3_BCM2835_GPIO_OFFSET + (bcm))

static int gpio_pin = -1;
module_param(gpio_pin, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH); 
MODULE_PARM_DESC(gpio_pin, "BCM GPIO pin number (e.g., 17)");

struct gpio_led_rpi3 {
	int linux_gpio;
	int bcm_gpio;
	struct gpio_desc *desc;
    struct led_classdev *led;
};

static struct gpio_led_rpi3 pin;

static void gpio_led_rpi3_brightness_set(struct led_classdev *led_cdev, enum led_brightness brightness) {
	pr_info("gpio_led_rpi3: Luminosité défini sur la LED %s à %d\n", led_cdev->name, brightness);

    if (brightness < 0 || brightness > 1) {
        pr_err("gpio_led_rpi3: Valeur incorrecte");
        return;
    }

    // Applique la nouvelle valeur à la LED
    gpiod_set_value(pin.desc, brightness);
    pr_info("gpio_pin_rpi3: GPIO %d (BCM %d) défini à %d\n", pin.linux_gpio, pin.bcm_gpio, brightness);
}

static enum led_brightness gpio_led_rpi3_brightness_get(struct led_classdev *led_cdev) {
	pr_info("Luminosité lu sur la LED %s, valeur actuelle: %d\n", led_cdev->name, led_cdev->brightness);
	return led_cdev->brightness;
}

static int register_rpi3_gpio_pin(void)
{
    if (gpio_pin < 0) {
        pr_err("gpio_led_rpi3: You must specify 'gpio_pin' (e.g., gpio_pin=17)\n");
        return -EINVAL;
    }

	pin.bcm_gpio = gpio_pin;
	pin.linux_gpio = BCM_TO_LINUX_GPIO(pin.bcm_gpio);

    // Récupération du descripteur GPIO à partir du numéro Globale Linux
    pin.desc = gpio_to_desc(pin.linux_gpio);
    if (!pin.desc) {
        pr_err("gpio_led_rpi3: Le GPIO %d (BCM %d) non trouvé\n", pin.linux_gpio, pin.bcm_gpio);
        return -ENODEV;
    }

    // Réclame le PIN GPIO
    if (gpiod_direction_output(pin.desc, 0)) {
        pr_err("gpio_led_rpi3: Impossible de configurer le GPIO %d\n", pin.linux_gpio);
		gpiod_put(pin.desc);
        return -EINVAL;
    }

    // Réinitialise la LED
    gpiod_set_value(pin.desc, 0);

    return 0;
}

static void unregister_rpi3_gpio_pin(void)
{
    // Turn LED off and release GPIO
    gpiod_set_value(pin.desc, 0);
    gpiod_put(pin.desc);
    pr_info("gpio_led_rpi3: GPIO %d (BCM %d) libéré (LED OFF)\n", pin.linux_gpio, pin.bcm_gpio);
}

static int register_rpi3_led(void)
{
    pin.led = kzalloc(sizeof(struct led_classdev), GFP_KERNEL);
    if (!pin.led) {
        pr_err("Échec de l'allocation de mémoire pour la LED virtuelle\n");
		return -ENOMEM;
    }

    pin.led->name = kasprintf(GFP_KERNEL, "rpi3-led:white:gpio-%d", pin.bcm_gpio);
    pin.led->color = LED_COLOR_ID_WHITE;
    pin.led->brightness = 0;
    pin.led->max_brightness = 1;
    pin.led->brightness_set = gpio_led_rpi3_brightness_set;
    pin.led->brightness_get = gpio_led_rpi3_brightness_get;

    int ret = led_classdev_register(NULL, pin.led);
	if (ret < 0) {
        kfree(pin.led->name);
        kfree(pin.led);
		pr_err("Impossible d'ajouter la LED virtuelle\n");
		return ret;
	}

    return 0;
}

static void unregister_rpi3_led(void)
{
    led_classdev_unregister(pin.led);
    kfree(pin.led->name);
    kfree(pin.led);
}

static int __init gpio_led_rpi3_init(void)
{
	int ret = register_rpi3_gpio_pin();
    if (ret != 0) {
        return ret;
    }

    ret = register_rpi3_led();
    if (ret != 0) {
        unregister_rpi3_gpio_pin();
        return ret;
    }

    return 0;
}

static void __exit gpio_led_rpi3_exit(void)
{
    unregister_rpi3_led();
    unregister_rpi3_gpio_pin();
}

module_init(gpio_led_rpi3_init);
module_exit(gpio_led_rpi3_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Florian RICHER <florian.richer@protonmail.com>");
MODULE_DESCRIPTION("Un module noyau pour utiliser un PIN GPIO d'une RPI en tant que LED");
MODULE_VERSION("1.0");