> break;
> case IOCTL_GET_NTH_BYTE:
> /* This ioctl is both input (ioctl_param) and
> * output (the return value of this function) */
> return Message[ioctl_param];
> break;
> }
> return SUCCESS;
>}
>/* Module Declarations *************************** */
>/* This structure will hold the functions to be called
>* when a process does something to the device we
>* created. Since a pointer to this structure is kept in
>* the devices table, it can't be local to
>* init_module. NULL is for unimplemented functions. */
>struct file_operations Fops = {
> NULL, /* seek */
> device_read,
> device_write,
> NULL, /* readdir */
> NULL, /* select */
> device_ioctl, /* ioctl */
> NULL, /* mmap */
> device_open,
>#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)
> NULL, /* flush */
>#endif
> device_release /* a.k.a. close */
>};
>/* Initialize the module - Register the character device */
>int init_module() {
> int ret_val;
> /* Register the character device (atleast try) */
> ret_val = module_register_chrdev(MAJOR_NUM, DEVICE_NAME, &Fops);
> /* Negative values signify an error */
> if (ret_val < 0) {
> printk("%s failed with %d\n", "Sorry, registering the character device ", ret_val);
> return ret_val;
> }
> printk("%s The major device number is %d.\n", "Registeration is a success", MAJOR_NUM);
> printk("If you want to talk to the device driver,\n");
> printk ("you'll have to create a device file. \n");
> printk ("We suggest you use:\n");
> printk ("mknod %s c %d 0\n", DEVICE_FILE_NAME, MAJOR_NUM);
> printk ("The device file name is important, because\n");
> printk ("the ioctl program assumes that's the\n");
> printk ("file you'll use.\n");
> return 0;
>}
>/* Cleanup - unregister the appropriate file from /proc */
>void cleanup_module() {
> int ret;
> /* Unregister the device */
> ret = module_unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
> /* If there's an error, report it */
> if (ret < 0) printk("Error in module_unregister_chrdev: %d\n", ret);
>}
chardev.h
>/* chardev.h - the header file with the ioctl definitions.
>*
>* The declarations here have to be in a header file,
>* because they need to be known both to the kernel
>* module (in chardev.c) and the process calling ioctl (ioctl.c)
>*/
>#ifndef CHARDEV_H
>#define CHARDEV_H #
>include
>/* The major device number. We can't rely on dynamic
>* registration any more, because ioctls need to know it. */
>#define MAJOR_NUM 100
>/* Set the message of the device driver */
>#define IOCTL_SET_MSG _IOR(MAJOR_NUM, 0, char *)
