Энциклопедия разработчика модулей ядра Linux

  /* Give the current message to the calling

  * process - the parameter we got is a pointer, fill it. */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

  i = device_read(file, (char*)ioctl_param, 99, 0);

#else

  i = device_read(inode, file, (char*)ioctl_param, 99);

#endif

  /* Warning - we assume here the buffer length is

  * 100. If it's less than that we might overflow

  * the buffer, causing the process to core dump.

  *

  * The reason we only allow up to 99 characters is

  * that the NULL which terminates the string also needs room. */

  /* Put a zero at the end of the buffer, so it will be properly terminated */

  put_user('\0', (char*)ioctl_param+i);

  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.

*