#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 

#include 



#define LEN 	1024	

struct scull{

	wait_queue_head_t r_que;

	wait_queue_head_t w_que;

	struct semaphore sem;

	struct cdev cdev;

	char buffer[LEN];

	dev_t devno;

	int count;

	int major;

	int minor;

};



struct scull *device;



static int com_read(struct file *filp,char __user *buf,size_t count,loff_t *pos)

{

	wait_event_interruptible(device->r_que,device->countsem);

	copy_to_user(buf,device->buffer,count);

	device->count=0;

	up(&device->sem);

}

static int com_write(struct file *filp,const char __user *buf,size_t count,loff_t *pos)

{

	down_interruptible(&device->sem);

	if(device->count>=LEN)

		wake_up_interruptible(&device->r_que);

	device->count+=count;

	copy_from_user(device->buffer+device->count,buf,count);

	up(&device->sem);

	return count;

}



static int com_open(struct inode *inode,struct file *filp)

{



	return 0;

}



static int com_release(struct inode *inode,struct file *filp)

{

	return 0;

}



struct file_operations f_ops=

{

	.owner=THIS_MODULE,

	.read=com_read,

	.write=com_write,

	.open=com_open,

	.release=com_release,

};



void set_cdev(void)

{

	int err;

	cdev_init(&device->cdev,&f_ops);

	device->cdev.owner=THIS_MODULE;

	device->cdev.ops=&f_ops;

	err=cdev_add(&device->cdev,device->devno,1);

	if(err)

		printk(KERN_INFO"Error %d adding dev n",err);

}



static int init(void)

{

	int ret;

	ret=alloc_chrdev_region(&device->devno,0,1,"block_file");

	if(retmajor=MAJOR(device->devno);

	device->minor=MINOR(device->devno);

	init_waitqueue_head(&device->r_que);

	init_waitqueue_head(&device->w_que);

	init_MUTEX(&device->sem);

	device->count=0;

	set_cdev();



	return 0;

}



static int exit(void)

{

	kfree(device);

	unregister_chrdev_region(device->devno,1);

	cdev_del(&device->cdev);

	return 0;

}



MODULE_LICENSE("Dual BSD/GPL");

module_init(init);

module_exit(exit);

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