counter/driver/counter.c

#include <linux/module.h>
#include <linux/init.h>
#include <linux/mod_devicetable.h>
#include <linux/property.h>
#include <linux/platform_device.h>
#include <linux/of_device.h>
#include <linux/gpio/consumer.h>
#include <linux/spi/spi.h>

/* Meta Information */
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Wolfgang Hottgenroth");
MODULE_DESCRIPTION("A simple LKM to parse the device tree for a specific device and its properties");

/* Declate the probe and remove functions */
static int dt_leds_probe(struct platform_device *pdev);
static void dt_leds_remove(struct platform_device *pdev);

static struct of_device_id leds_driver_ids[] = {
  {
    .compatible = "hottis,leds",
  }, { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, leds_driver_ids);

static struct platform_driver leds_driver = {
  .probe = dt_leds_probe,
  .remove = dt_leds_remove,
  .driver = {
    .name = "leds_device_driver",
    .of_match_table = leds_driver_ids,
  },
};

/* GPIO variable */
static struct gpio_desc *red_led = NULL;
static struct gpio_desc *blue_led = NULL;


/* spi stuff */
static int dt_ls7366r_probe(struct spi_device *client);
static void dt_ls7366r_remove(struct spi_device *client);

static struct of_device_id ls7366r_driver_ids[] = {
  {
    .compatible = "hottis,ls7366r",
  }, {}
};
MODULE_DEVICE_TABLE(of, ls7366r_driver_ids);

static struct spi_device_id ls7366r[] = {
  { "ls7366r", 0 },
  {},
};
MODULE_DEVICE_TABLE(spi, ls7366r);

static struct spi_driver ls7366r_driver = {
  .probe = dt_ls7366r_probe,
  .remove = dt_ls7366r_remove,
  .id_table = ls7366r,
  .driver = {
    .name = "ls7366r_device_driver",
    .of_match_table = ls7366r_driver_ids,
  },
};

/**
 * @brief This function is called on loading the driver 
 */
static int dt_leds_probe(struct platform_device *pdev) {
  struct device *dev = &pdev->dev;

  printk("counter - leds probing\n");

  if(!device_property_present(dev, "red-led-gpio")) {
    printk("counter - Error! Device property 'red-led-gpio' not found!\n");
    return -1;
  }
  if(!device_property_present(dev, "blue-led-gpio")) {
    printk("counter - Error! Device property 'blue-led-gpio' not found!\n");
    return -1;
  }


  /* Init GPIO */
  red_led = gpiod_get(dev, "red-led", GPIOD_OUT_LOW);
  if(IS_ERR(red_led)) {
    printk("counter - Error! Could not setup the GPIO red-led\n");
    return -1 * IS_ERR(red_led);
  }
  blue_led = gpiod_get(dev, "blue-led", GPIOD_OUT_LOW);
  if(IS_ERR(blue_led)) {
    printk("counter - Error! Could not setup the GPIO blue-led\n");
    return -1 * IS_ERR(blue_led);
  }

  return 0;
}

/**
 * @brief This function is called on unloading the driver 
 */
static void dt_leds_remove(struct platform_device *pdev) {
  printk("counter - leds removing\n");
  gpiod_put(red_led);
  gpiod_put(blue_led);
}

static int dt_ls7366r_probe(struct spi_device *client) {
  printk("counter - ls7366r probing\n");
  
  int ret = spi_setup(client);
  if (ret < 0) {
    printk("counter - Error! Failed to set up the SPI bus\n");
    return ret;
  }

  return 0;
}


static void dt_ls7366r_remove(struct spi_device *client) {
  printk("counter - ls7366r removing\n");
}


/**
 * @brief This function is called, when the module is loaded into the kernel
 */
static int __init my_init(void) {
  printk("counter - Loading the leds driver...\n");
  if(platform_driver_register(&leds_driver)) {
    printk("dt_gpio - Error! Could not load driver\n");
    return -1;
  }

  printk("counter - Loading the ls7366r driver...\n");
  if (spi_register_driver(&ls7366r_driver)) {
    printk("counter - Error! Could not load spi driver\n");
    return -1;
  }

  printk("counter - red led on\n");
  gpiod_set_value(red_led, 1);

  return 0;
}

/**
 * @brief This function is called, when the module is removed from the kernel
 */
static void __exit my_exit(void) {
  printk("counter - red led off\n");
  gpiod_set_value(red_led, 0);

  printk("counter - Unloading the leds driver...\n");
  platform_driver_unregister(&leds_driver);

  printk("counter - Unloading the ls7366r driver...\n");
  spi_unregister_driver(&ls7366r_driver);
}

module_init(my_init);
module_exit(my_exit);