copy_to_user and copy_from_user

guruteck_at_gmail.com
Date: 01/18/05 

Date: 18 Jan 2005 03:44:47 -0800

Hi Guys

I wrote a simple character driver with read and write functions
as below.I first used copy_to_user/copy_from_user .then replaced them
with simple coping as below.It just writes a word to device and gets a
word from device.

char *k;
int MyRead(struct file *filep,char *buf,size_t size,loff_t *offp)
{
int i;
/* copy_to_user(buf,k,4);*/
for(i=0;i<4;i++)
buf[i]=k[i];
}
int MyWrite(struct file *filp,char *buff,size_t count,loff_t *offp)
{
int i;

k=(char *)kmalloc(4,GFP_KERNEL);
/*copy_from_user(k,buff,4);*/
for(i=0;i<4;i++)
k[i]=buff[i];
}

But Without Using copy_to_user/copy_from_user this function is working
properly
I didnt get its behaviour.
Is this mean can we write driver without using
copy_to_user/copy_from_user functions???Then what is the use of these
functions..???

Thanx in advance for any help

Regards