字符设备驱动程序的创建实例

call_app.c

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

#define DEVICE_FILENAME "/dev/calldev"

int main()
{
	int dev;
	char buff[128];
	int ret;

	printf("1) device file open\n");

	dev=open(DEVICE_FILENAME,O_RDWR|O_NDELAY);
	if(dev>=0)
	{
		printf("2)seek function call\n");

		ret =lseek(dev,0x20,SEEK_SET);
		printf("ret=%08X\n",ret);
		printf("3)read function call \n");

		ret=read(dev,0x30,0x31);
		printf("ret=%08X\n",ret);

		printf("4) write function call\n");
		ret=write(dev,0x40,0x41);
		printf("ret=%08X\n",ret);

		printf("5)ioctl function call\n");
		ret=ioctl(dev,0x51,0x52);
		printf("ret=%08X\n",ret);

		printf("6)device file close\n");
		ret=close(dev);
		printf("ret=%08X\n",ret);

			}
         return 0;
  }

call_dev.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/fcntl.h>

#define CALL_DEV_NAME "calldev"
#define CALL_DEV_MAJOR 240

int call_open(struct inode *inode ,struct file *filp)
{
   int num = MINOR(inode->i_rdev);
	 printk("call open->minor:%d\n",num);
	 return 0;
}

loff_t call_llseek(struct file *filp,loff_t off,int whence)
{
	printk("call llseek->off:%08X,whence:%08X\n",off,whence);
	return 0x23;
}
ssize_t call_read(struct file *filp,char *buf,size_t count,loff_t *f_pos)
{
	printk("call read->buf:%08X,count:%08X\n",buf,count);
	return 0x33;
}
ssize_t call_write(struct file *filp,const char *buf,size_t count,loff_t *f_pos)
{
	printk("call write->buf :%08X,count:%08X\n",buf,count);
 	return 0x43;
}

int call_ioctl(struct inode *inode,struct file *filp,unsigned int cmd,unsigned long arg)
{
	printk("call ioctl -> cmd:%08X,arg:%08X\n",cmd,arg);
	return 0x53;
}
int call_release(struct inode *inode ,struct file *filp)
{
	printk("call release\n");
	return 0;
}

struct file_operations call_fops =
{
	.owner=THIS_MODULE,
	.llseek=call_llseek,
	.read=call_read,
	.write=call_write,
	.unlocked_ioctl=call_ioctl,
	.open=call_open,
	.release=call_release,
};


int call_init (void)
{
	 int result;
	 printk("call call_init \n");
	//call_fops.ioctl = call_ioctl;
	 result=register_chrdev(CALL_DEV_MAJOR,CALL_DEV_NAME,&call_fops);
	 if(result<0) return result;
	 return 0;

}

void call_exit (void)
{
	printk("call call_exit \n");
	unregister_chrdev(CALL_DEV_MAJOR,CALL_DEV_NAME);

}
 
 module_init (call_init);
 module_exit (call_exit);

 MODULE_LICENSE("DUAL BSD /GPL");
 

Makefile

obj-m:=call_dev.o
KDIR :=/lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)

default:
  $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

clean:
	rm -rf *.ko
	rm -rf *.mod.*
	rm -rf .*.cmd
	rm -rf *.o	

step

mknod /dev/calldev c 240 32
make
insmod call_dev.ko
lsmod
gcc -o call_app call_app.c
./call_app.c
dmesg
rmmod call_dev