2.6内核字符设备驱动程序解析

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/cdev.h>

#include <linux/fs.h>

#include <linux/sched.h>

#include <asm/uaccess.h>

MODULE_LICENSE("GPL");

MODULE_AUTHOR("lan");

#define DP_MAJOR 251//主设备号

#define DP_MINOR 0  //次设备号

static int char_read(struct file *filp, char __user *buffer, size_t, loff_t*);

static int char_open(struct inode*, struct file*);

static int char_write(struct file *filp, const char __user *buffer, size_t, loff_t*);

static int char_release(struct inode*, struct file*);

static int chropen;

struct cdev *chardev;

static int len;

static char *to;

static const struct file_operations char_ops={

.read = char_read,

.write = char_write,

.open = char_open,

.release = char_release,

};

static int __init char_init(void)

{

dev_t dev;

printk(KERN_ALERT"Initing......\n");

dev = MKDEV(DP_MAJOR, DP_MINOR);

chardev = cdev_alloc();

if(chardev == NULL){

return -1;

}

if(register_chrdev_region(dev, 10, "chardev")){

printk(KERN_ALERT"Register char dev error\n");

return -1;

}

chropen = 0;

len = 0;

cdev_init(chardev, &char_ops);

if(cdev_add(chardev, dev, 1)){

printk(KERN_ALERT"Add char dev error!\n");

}

return 0;

}

static int char_open(struct inode *inode, struct file *file)

{

if(chropen == 0)

chropen++;

else{

printk(KERN_ALERT"Another process open the char device\n");

return -1;

}

try_module_get(THIS_MODULE);

return 0;

}

static int char_release(struct inode *inode,struct file *file)

{

chropen--;

module_put(THIS_MODULE);

return 0;

}

static int char_read(struct file *filp,char __user *buffer,size_t length,loff_t *offset)

{

unsigned long nn;

nn = copy_to_user(buffer, to, length);

printk("nn = %ld\n", nn);

printk("buffer = %s\n", buffer);

return length;

}

static int char_write(struct file *filp, const char __user *buffer, size_t length, loff_t *offset)

{

unsigned long n;

to = (char *)kmalloc((sizeof(char)) * (length+1), GFP_KERNEL);

memset(to, '\0', length+1);

n = copy_from_user(to, buffer, length);

printk("n = %ld\n", n);

printk("to = %s\n", to);

return length;

}

static void __exit module_close(void)

{

len=0;

printk(KERN_ALERT"Unloading..........\n");

unregister_chrdev_region(MKDEV(DP_MAJOR,DP_MINOR),10);

cdev_del(chardev);

}

module_init(char_init);

module_exit(module_close);

obj-m += chardev.o

all:

make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:

make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <fcntl.h>

int main(int args, char *argv[])

{

int testdev;

int i, rf = 0;

char buf[15];

memset(buf, '\0', 15);

testdev = open("/dev/chardev0", O_RDWR);

if(testdev == -1){

perror("open\n");

exit(0);

}

if((write(testdev, "1111111111", 10)) < 0){

perror("Write error!\n");

exit(0);

}

close(testdev);

printf("write finish!\n");

testdev = open("/dev/chardev0", O_RDWR);

rf = read(testdev, buf, 3);

if(rf < 0)

perror("read error\n");

printf("Read: %s\n", buf);

close(testdev);

return 0;

}