Re: Simple Misc Driver - Problem with string copy to user

Lucas Tanure <tanure@linux.com> writes:

...

What is worg with my read operation?

static ssize_t misc_drv_read(struct file *filp, char __user * buf, size_t count, loff_t * offp){ int nbytes; char * string = "hello World"; nbytes = copy_to_user(buf, string, 12); return nbytes; }

copy_to_user returns the number of bytes which could *not* be copied. So it will return 0 on success, making your read return 0. Bjørn