Энциклопедия разработчика модулей ядра Linux

Померанц Ори

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 <linux/ioctl.h>

/* 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 <fcntl.h> /* open */

#include <unistd.h> /* exit */