So, My misc_drv_read returns 0, and it's ok. So why the command head didn't get the string ?
-- Lucas Tanure +55 (19) 988176559 On Tue, May 27, 2014 at 9:59 AM, Bjørn Mork <[email protected]> wrote: > Lucas Tanure <[email protected]> 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 >
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