EPSIAE » eneraptor

/*

* 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.

*/

/*

* device specifics, such as ioctl numbers and the

* major device file.

*/

#include "chardev.h"

#include <stdio.h>

#include <stdlib.h>

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

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

#include <sys/ioctl.h>        /* 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);

}

ioctl_get_nth_byte(int file_desc)

{

        int i;

        char c;

        printf("get_nth_byte message:");

        i = 0;

        do {

                c = ioctl(file_desc, IOCTL_GET_NTH_BYTE, i++);

                if (c < 0) {

                        printf("ioctl_get_nth_byte failed at the %d'th byte:\n",i);

                        exit(-1);

                }

                putchar(c);

        } while (c != 0);

        putchar('\n');

}

/*

* Main − Call the ioctl functions

*/

main()

{

        int file_desc, ret_val;

        char *msg = "Message passed by ioctl\n";

        file_desc = open(DEVICE_FILE_NAME, 0);

        if (file_desc < 0) {

                printf("Can't open device file: %s\n", DEVICE_FILE_NAME);

                exit(-1);

        }

        ioctl_set_msg(file_desc, msg);

        ioctl_get_nth_byte(file_desc);

        ioctl_get_msg(file_desc);

        close(file_desc);

}