chardev_app.c

在linux环境下的字符设备驱动程序。具有最基本的设备的读和写功能

#include <stdio.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>

#define MAJOR_NUM 252
#define IOCTL_SET_MSG _IOW(MAJOR_NUM, 0, int *)
#define IOCTL_GET_MSG _IOR(MAJOR_NUM, 1, int *)
int main()
{
	int fp;
	char str[100];
	unsigned long ptr;

	fp=open("chardev", O_RDWR);
	ioctl(fp, IOCTL_GET_MSG, &ptr);
	read(fp, str, 80);
	str[80]='\0';
	printf("\nMessage %d reads:%s\n", ptr, str);

	ptr++;
	if (ptr>3) ptr=1;
	ioctl(fp, IOCTL_SET_MSG, ptr);
	close(fp);
	return 0;
}