Re: [PATCH] USB: note that usb_fill_int_urb() can be used used for ISOC urbs.

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On 2018-06-20 11:35:05 [-0400], Alan Stern wrote:
> > diff --git a/include/linux/usb.h b/include/linux/usb.h
> > index 4cdd515a4385..c3a8bd586121 100644
> > --- a/include/linux/usb.h
> > +++ b/include/linux/usb.h
> > @@ -1657,7 +1657,8 @@ static inline void usb_fill_bulk_urb(struct urb *urb,
> >   *	the endpoint descriptor's bInterval value.
> >   *
> >   * Initializes a interrupt urb with the proper information needed to submit
> > - * it to a device.
> > + * it to a device. This function can also be used to initialize an isochronous
> > + * urb.
> 
> No, no!  This function can _help_ initialize an isochronous URB, but
> that's all.  It would be better to create an explicit 
> usb_fill_isoc_urb() routine, and even that would have to be incomplete.

Yes, incomplete. I read incomplete as some additional fields have to be
set which are not set yet. But for FS you write…

> There are two problems with using usb_fill_int_urb() to initialize an 
> isochronous URB:
> 
> 	The calculation of the interval value is wrong for full-speed
> 	devices.

Why wrong?

> 	The routine does not set urb->number_of_packets or
> 	urb->iso_frame_desc[].

Yes.

> Alan Stern

Sebastian



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