#include <linux/fs.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>

#define DRIVER_MAJOR 240

MODULE_LICENSE("GPL");

static struct file_operations fops;
static DECLARE_COMPLETION( dev_obj_is_free );
static int frequenz; // Zustandsvariable des Gerätes

static void mydevice_release( struct device *dev )
{
    complete( &dev_obj_is_free );
}

struct platform_device mydevice = {
    .name  = "MyDevice",
    .id    = 0,
    .dev = {
        .release = mydevice_release,
    }
};

static struct device_driver mydriver = {
    .name = "MyDevDrv",
    .bus = &platform_bus_type,
};

static ssize_t read_freq( struct device *dev, char *buf )
{
    snprintf(buf, 256, "frequenz: %d", frequenz ); 
    return strlen(buf)+1;
}

static ssize_t write_freq( struct device *dev, const char *buf, size_t count )
{
    frequenz = simple_strtoul( buf, NULL, 0 );
    return strlen(buf)+1;
}

static DEVICE_ATTR( freq ,S_IRUGO|S_IWUGO, read_freq, write_freq );

static int __init drv_init(void)
{
    if(register_chrdev(DRIVER_MAJOR, "MyDevice", &fops) == 0) {
        driver_register(&mydriver);           // register the driver
        platform_device_register( &mydevice );// register the device
        mydevice.dev.driver = &mydriver;      // now tie them together
        device_bind_driver( &mydevice.dev );  // links the driver to the device
        device_create_file( &mydevice.dev, &dev_attr_freq );
        return 0;
    }
    return -EIO;
}

static void __exit drv_exit(void)
{
    device_remove_file( &mydevice.dev, &dev_attr_freq );
    device_release_driver( &mydevice.dev );
    platform_device_unregister( &mydevice );
    driver_unregister(&mydriver);
    unregister_chrdev(DRIVER_MAJOR,"MyDevice");
    wait_for_completion( &dev_obj_is_free );
}

module_init( drv_init );
module_exit( drv_exit );