Open return value - segmentation fault

["Vijay Ram Chitrapu (RCVIJAYD)" <cvijay@xxxxxxxxxxxxxxxxxx>]

Hi all,
  I have a query regarding the file descriptor obtained from the open 
call. I have written a dummy driver code which has open, ioclt and release 
file operations to it. In the open, i am returning 0. In the user space 
when i open the device , i get an fd as 3. When i perform an ioctl with 
the same fd  to the device, a segmentation fault of NULL pointer derefence 
is thrown. I have tried return 1 in the open and everything worked well. 
Can anyone please tell me in what way is the return value of open related 
to the file descriptor. 
The code is below for reference..

static struct file_operations this_fops = {
	open:this_open,
	ioctl:this_ioctl,
	release:this_release,
};

int this_open (struct inode *ino, struct file *fp)
{
 printk("<1> in open");
 return 0;
}

int this_ioctl(struct inode * ino, struct file *fp, unsigned int cmd, 
unsigned long len)
{
  printk("<1> in ioctl function);
  return 1;
}



Thanks In Advance
Vijay Ram.C



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