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

static char *device_label = "";
module_param(device_label, charp, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); 
MODULE_PARM_DESC(device_label, "GPIO Device Label");

static char *gpio_pin_id = "";
module_param(gpio_pin_id, charp, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); 
MODULE_PARM_DESC(gpio_pin_id, "GPIO Pin ID");

struct gpio_device *device;
struct gpio_desc *led_desc;

// Copied from https://elixir.bootlin.com/linux/v6.6.79/source/drivers/gpio/gpiolib.c#L1085
// gpio_device_find_by_label it's not available on Linux Kernel 6.6 but only with Linux Kernel 6.7+
// static int gpiochip_match_name(struct gpio_chip *gc, void *data)
// {
// 	const char *name = data;

// 	return !strcmp(gc->label, name);
// }

static int __init gpio_led_init(void) {
	int ret;

	// On Linux Kernel 6.7+
	device = gpio_device_find_by_label(device_label);
	// Otherwise
	// device = gpio_device_find(device_label, gpiochip_match_name);
	if (!device) {
		pr_err("Failed to get device");
		return -ENODEV;
	}

	led_desc = gpiod_get(device->dev, gpio_pin_id, GPIOD_OUT_LOW);
	if (IS_ERR(led_desc)) {
		pr_err("Failed to get GPIO: %ld\n", PTR_ERR(led_desc));
		ret = PTR_ERR(led_desc);
		goto fail;
	}

	gpiod_set_value(led_desc, 1);

	pr_info("Bonjour! Le module est chargé.\n");
	return 0;

fail:
	gpio_device_put(device);
	return -ENODEV;
}

static void __exit gpio_led_exit(void) {
	gpiod_set_value(led_desc, 0);

	gpiod_put(led_desc);
	gpio_device_put(device);

	pr_info("Au revoir! Le module est déchargé.\n");
}

module_init(gpio_led_init);
module_exit(gpio_led_exit);

MODULE_LICENSE("MIT License");
MODULE_AUTHOR("Florian RICHER");
MODULE_DESCRIPTION("Un module noyau pour utiliser un PIN GPIO d'une RPI en tant que LED");
MODULE_VERSION("1.0");