Re: how can i make the skeleton read function blocking function?

Am Dienstag, 24. April 2007 12:06 schrieb Wael Adel:
> On 4/24/07, Oliver Neukum <[email protected]> wrote:
> > Am Dienstag, 24. April 2007 11:46 schrieb Wael Adel:
> > >         retval = usb_submit_urb(urb, GFP_KERNEL);
> > >         if (retval) {
> > >                 err("%s - failed submitting write urb, error %d",
> > __FUNCTION__, retval);
> > >                 goto error;
> > >         }
> > >
> > >         if (buf != NULL)
> > >         {
> > >                 if (copy_to_user(user_buffer, buf , readsize))
> > >                 {
> > >                         retval = -EFAULT;
> > >                         goto error;
> > >                 }
> > >         }
> >
> > You are copying the the buffer to user space without waiting for the
> > URB to be executed. That cannot work.
> 
> so how can i wait for the urb to be executed then copying the data to
> the user space?
> is there a flag that i should loop on it or what?

- init an instance of "struct completion"
- submit the URB, passing a pointer to the struct completion
- use wait_for_completion()

- in the completion handler call complete()

	HTH
		Oliver
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