static ssize_t device_write(struct file *file, const char __user *buffer, size_t length, loff_t *offset)
{
    DBG("device write attempt\n");
    DBG_FMT("length: %i\n", length);
    //struct packet _x;
    //struct packet *foo = &_x;
    struct packet foo;
    DBG_FMT("size should be greater than %i but less than %i - it is: %i\n", sizeof(struct packet) - DATA_MAX, sizeof(struct packet), length);
    if ((length > sizeof(struct packet)) || (length <= (sizeof(struct packet) - DATA_MAX))) // too much or no payload
        return -EINVAL;
    DBG_FMT("allocated memory variable is assigned to: %i", sizeof(foo));
    if (copy_from_user(&foo, buffer, length))
        return -EFAULT;
    foo.data[length - (sizeof(struct packet) - DATA_MAX)] = '\0'; // set 0-Byte to end of string
    DBG_FMT("  header :: duration: %i, count: %i\n", foo.duration, foo.count);
    DBG_FMT("  payload :: as string: < %s >\n", foo.data);

    //if (!rfm12_ask_modulate(foo))
    //    return -EINVAL;

    DBG_FMT("return: %i\n", length);
    return length;
}