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

#define DRIVER_MAJOR 240

MODULE_LICENSE("GPL");

static struct file_operations Fops;
static DECLARE_COMPLETION( DevObjectIsFree );
static int Frequenz; // Zustandsvariable des Gerätes

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

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 ReadFreq( struct device *dev, char *buf )
{
    sprintf(buf, "Frequenz: %d", Frequenz ); 
    return strlen(buf)+1;
}

static ssize_t WriteFreq( 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, ReadFreq, WriteFreq );


static int __init DrvInit(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 ); // attributes
        return 0;
    }
    return -EIO;
}

static void __exit DrvExit(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( &DevObjectIsFree );
}

module_init( DrvInit );
module_exit( DrvExit );