kernel-playground/dummy-gpio/dummy-gpio.c

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

struct dummy_gpio {
  struct gpio_chip gc;
  struct mutex lock;
};


static struct dummy_gpio dgpio;
  
static int dummy_gpio_direction_input(struct gpio_chip *chip, unsigned offset) {
  printk("direction input\n");
  return 0;
}

static void dummy_gpio_set(struct gpio_chip *chip, unsigned offset, int value) {
  printk("set\n");
}

static int dummy_gpio_direction_output(struct gpio_chip *chip, unsigned offset, int value) {
  printk("output\n");
  return 0;
}

static int dummy_gpio_get(struct gpio_chip *chip, unsigned offset) {
  printk("get\n");
  return 0;
}

static int __init dummy_gpio_init(void) {
  int err;

  mutex_init(&dgpio.lock);
  dgpio.gc.label = "dummy_gpio";
  dgpio.gc.direction_input = dummy_gpio_direction_input;
  dgpio.gc.get = dummy_gpio_get;
  dgpio.gc.direction_output = dummy_gpio_direction_output;
  dgpio.gc.set = dummy_gpio_set;

  dgpio.gc.ngpio = 8;
  dgpio.gc.can_sleep = true;
  // from 4.5 
  dgpio.gc.parent = NULL;
  // dgpio.gc.dev = NULL;
  dgpio.gc.owner = THIS_MODULE;

  //  gpiochip_add_data from 4.5
  err = gpiochip_add(&dgpio.gc);
  //err = gpiochip_add_data()
  if(err)
    goto exit_destroy;
  return err;
 exit_destroy:
  mutex_destroy(&dgpio.lock);
  return err;
}

static void __exit dummy_gpio_exit(void) {
  gpiochip_remove(&dgpio.gc);
  mutex_destroy(&dgpio.lock);
  printk("dummy_gpio: Cya in another life\n");
}

module_init(dummy_gpio_init);
module_exit(dummy_gpio_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("encrypt";)
MODULE_DESCRIPTION("Dummy gpiochip");