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

/*
 * Last compiled with Linux 6.14.5-300.fc42.x86_64
 */

/* Meta Info */
MODULE_DESCRIPTION("Demo kernel module.");
MODULE_VERSION("0.0.1");
MODULE_AUTHOR("Imbus");
MODULE_LICENSE("GPL");

/*
 * Hard coded for RPI3
 * Usually retrieved via device tree
 */
#define IO_LED 21
#define IO_BUTTON 20
#define IO_OFFSET 0

static struct gpio_desc *led, *button;

/**
 * @brief Called on load
 */
static int __init demo_mod_init(void) {
  printk(KERN_INFO "Demo module loaded successfully...");

  int status;

  led = gpio_to_desc(IO_LED + IO_OFFSET);
  if (!led) {
    printk("gpioctrl - Error getting pin 21\n");
    return -ENODEV;
  }

  button = gpio_to_desc(IO_BUTTON + IO_OFFSET);
  if (!button) {
    printk("gpioctrl - Error getting pin 20\n");
    return -ENODEV;
  }

  status = gpiod_direction_output(led, 0);
  if (status) {
    printk("gpioctrl - Error setting pin 20 to output\n");
    return status;
  }

  status = gpiod_direction_input(button);
  if (status) {
    printk("gpioctrl - Error setting pin 21 to input\n");
    return status;
  }

  gpiod_set_value(led, 1);

  printk("gpioctrl - Button is %spressed\n",
         gpiod_get_value(button) ? " " : "not ");

  return 0;
}

/**
 * @brief Called on unload
 */
static void __exit demo_mod_exit(void) {
  printk(KERN_INFO "Demo module unloaded successfully...");
}

module_init(demo_mod_init);
module_exit(demo_mod_exit);