chrdev.c

一个基于linux的内核操作编程文件

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <linux/ioctl.h>
#include "chrdev_stanley.h"
#define DEVICE_NAME "chrdev"
#ifdef CONFIG_DEVFS_FS
#include <linux/devfs_fs_kernel.h>
#endif

#ifdef HELLO_DEBUG
#include <linux/proc_fs.h>
#endif
int pointer;

char *string;

char *msg1="This is an kernel module example string1-----------------\n";
char *msg2="This is an kernel module example string2-----------------\n";
char *msg3="This is an kernel module example string3-----------------\n";

int hello_open(struct inode *node, struct file *filp)
{
//	printk("major and minor device number=%x\n", node->i_rdev);
//	printk("Major number=%d\n", MAJOR(node->i_rdev));
	printk("Device is open\n");
	pointer=0;
	return 0;
}

int hello_close(struct inode *node, struct file *filp)
{
	printk("Device is closed\n");
	return 0;
}

ssize_t hello_read(struct file *filp, char *buffer, size_t length, loff_t *offset)
{
	printk("Read data from kernelspace to userspace\n");
	if(pointer==0)
	{
		copy_to_user(buffer, string, 40);
		pointer=40;
		return 40;
	}else
		return 0;
}

ssize_t hello_write(struct file *filp, const char *buffer, size_t length, loff_t *offset)
{
	printk("Write data from userspace to kernelspace\n");
	copy_from_user(string, buffer, length);
	return length;
}

int hello_ioctl(struct inode *node, struct file *filp, unsigned int cmd, unsigned long arg)
{
	switch(cmd)
	{
		case IOCTL_SET_MSG:
			if (arg==1) string=msg1;
			if (arg==2) string=msg2;
			if (arg==3) string=msg3;
			break;
		case IOCTL_GET_MSG:
			if (string==msg1) *(long *)arg=1;
			if (string==msg2) *(long *)arg=2;
			if (string==msg3) *(long *)arg=3;
		default:
			break;
	}
	return 0;
}

int major;

struct file_operations fops={
       open : hello_open,
       release : hello_close,
       read : hello_read,
       write: hello_write,
       ioctl: hello_ioctl
};

#ifdef HELLO_DEBUG
int hello_read_proc(char *buf, char **start, off_t offset,
		                   int count, int *eof, void *data)
{
	sprintf(buf, "Test Device proc mechanism.\n");
	*eof=1;
	return strlen(buf);
}
static void hello_create_proc()
{
	create_proc_read_entry("hello_char", 0 /* default mode */,
			NULL /* parent dir */, hello_read_proc,
			NULL /* client data */);
}
static void hello_remove_proc()
{
	/* no problem if it was not registered */
	remove_proc_entry("hello_char", NULL /* parent dir */);
}

#endif

int init_module()
{
	string=msg1;
	major=register_chrdev(MAJOR_NUM, DEVICE_NAME, &fops);
	if ( major>0 ) printk("\n\nMajor=%d\n", major);
	else if ( major < 0) {
		printk ("Can't register this module\n");
		unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
		return 1;
	}

#ifdef CONFIG_DEVFS_FS
	devfs_hello_dir = devfs_mk_dir (NULL, "hello", NULL);
	devfs_helloraw = devfs_register (devfs_hello_dir, "hello", 
			DEVFS_FL_DEFAULT, MAJOR_NUM, MINOR_NUM, S_IFCHR | S_IRUSR | S_IWUSR,
			&fops, NULL );
#endif
#ifdef HELLO_DEBUG /* only when debugging */
	hello_create_proc();
#endif
	return 0;
}

void cleanup_module()
{
	string=msg1;
#ifdef CONFIG_DEVFS_FS
	unregister (devfs_helloraw);
#endif
#ifdef HELLO_DEBUG /* only when debugging */
//	hello_remove_proc();
#endif
	unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
}


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stanley Peng");