Энциклопедия разработчика модулей ядра Linux

* 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 *)

/* _IOR means that we're creating an ioctl command

* number for passing information from a user process

* to the kernel module.

*

* The first arguments, MAJOR_NUM, is the major device

* number we're using.

*

* The second argument is the number of the command

* (there could be several with different meanings).

*

* The third argument is the type we want to get from

* the process to the kernel. */

/* Get the message of the device driver */

#define IOCTL_GET_MSG _IOR(MAJOR_NUM, 1, char *)

/* This IOCTL is used for output, to get the message

* of the device driver. However, we still need the

* buffer to place the message in to be input,

* as it is allocated by the process. */

/* Get the n'th byte of the message */

#define IOCTL_GET_NTH_BYTE _IOWR(MAJOR_NUM, 2, int)

/* The IOCTL is used for both input and output. It

* receives from the user a number, n, and returns Message[n]. */

/* The name of the device file */

#define DEVICE_FILE_NAME "char_dev"

#endif  

ioctl.c 

/* ioctl.c - the process to use ioctl's to control the

* kernel module

*

* Until now we could have used cat for input and

* output. But now we need to do ioctl's, which require

* writing our own process. */

/* Copyright (C) 1998 by Ori Pomerantz */

/* device specifics, such as ioctl numbers and the major device file. */

#include "chardev.h"

#include /* open */

#include /* exit */

#include /* ioctl */

/* Functions for the ioctl calls */

ioctl_set_msg(int file_desc, char *message) {

 int ret_val;

 ret_val = ioctl(file_desc, IOCTL_SET_MSG, message);

 if (ret_val < 0) {

  printf("ioctl_set_msg failed:%d\n", ret_val);

  exit(-1);

 }

}

ioctl_get_msg(int file_desc) {

 int ret_val;

 char message[100];

 /* Warning - this is dangerous because we don't tell

 * the kernel how far it's allowed to write, so it

 * might overflow the buffer. In a real production

 * program, we would have used two ioctls - one to tell

 * the kernel the buffer length and another to give

 * it the buffer to fill */

 ret_val = ioctl(file_desc, IOCTL_GET_MSG, message);

 if (ret_val < 0) {

  printf("ioctl_get_msg failed:%d\n", ret_val);

  exit(-1);

 }

 printf("get_msg message:%s\n", message);

}