skull.c

一个Linux系统字符驱动的源代码

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <asm/uaccess.h>

unsigned int fs_major=0;
static char *data;

static ssize_t test_read(struct file*,char*,size_t,loff_t*);
static ssize_t test_write(struct file*,char*,size_t,loff_t*);
static int test_open(struct inode*,struct file*);
static int test_release(struct inode*,struct file*);
static struct file_operations chr_fops=
{
	read: test_read,
	write: test_write,
	open: test_open,
	release: test_release,
};

static ssize_t test_read(struct file *file,char *buf,size_t count,loff_t *f_pos)
{
	int len;
	if(count<0)
		return -EINVAL;
	len=strlen(data);
	if(len<count)
		count=len;
	copy_to_user(buf,data,count+1);
	return count;
}

static ssize_t test_write(struct file *file,char *buf,size_t count,loff_t *f_pos)
{
	if(count<0)
		return -EINVAL;
	kfree(data);
	data=(char *)kmalloc(sizeof(char)*(count+1),GFP_KERNEL);
	
	if(!data)
		return -ENOMEM;

	copy_from_user(data,buf,count+1);
	return count;
}

static ssize_t test_open(struct inode *inode,struct file *file)
{
//	MOD_INC_USE_COUNT;
	printk("This is open\n");
	return 0;
}

static ssize_t test_release(struct inode *inode,struct file *file)
{
//	MOD_INC_USE_COUNT;
	printk("This is released\n");
	return 0;
}

int skull_init(void)
{
	int res;
	res=register_chrdev(0,"szx",&chr_fops);
	if(res<0)
	{
		printk("can't get major name!\n");
		return res;
	}	
	if(fs_major==0)
		fs_major=res;
     
        printk("module init!\n"); 
	return 0;
}
void skull_exit(void)
{
	unregister_chrdev(fs_major,"szx");
        printk("module clean up!\n");
}
module_init(skull_init); 
module_exit(skull_exit);