Re: [PATCH] usb: core: allow zero packet flag for interrupt urbs

[Amit Virdi]

On 7/18/2014 8:09 PM, Alan Stern wrote:
> On Fri, 18 Jul 2014, Amit Virdi wrote:
>
> > On 7/17/2014 8:25 PM, Alan Stern wrote:
> > > I can't say this is actually wrong, but have you ever encountered a
> > > situation where this would be needed?  How often does anyone need to do
> > > a multi-packet transfer over an interrupt endpoint?
> >
> > Honestly, I haven't found any such real device yet. I did this change
> > while I was going through the code when adding support for interrupt
> > transfers in gadget zero. I'm a no expert, but the spec says it should
> > be supported so this code should be added.
>
> I just remembered, the HID spec requires that all reports (except the
> longest) end with a short packet.  And since output reports are allowed
> to be sent over an Interrupt-OUT endpoint, we have to accept the
> URB_ZERO_PACKET flag for interrupt URBs.

Ok, great!

> > However, I messed up a little in this patch. It should have been
> > ---
> >           case USB_ENDPOINT_XFER_ISOC:
> >                   allowed |= URB_ISO_ASAP;
> >                   break;
> > +       case USB_ENDPOINT_XFER_INT:
> > +               if (is_out)
> > +                       allowed |= URB_ZERO_PACKET;
> > +               else
> > +                       allowed |= URB_SHORT_NOT_OK;
> > +               break;
> >           }
> >           allowed &= urb->transfer_flags;
> >
> > ---
> > Otherwise, it sets zero packet flag for control out transfers too.
> >
> > I'll send a V2 with this change if you agree to setting of the zero
> > packet flag for interrupt transfers.
>
> How about this change instead?
>
>   			URB_FREE_BUFFER);
>   	switch (xfertype) {
>   	case USB_ENDPOINT_XFER_BULK:
> +	case USB_ENDPOINT_XFER_INT:

Looks better.
I'll submit a V2 with this change.

Regards
Amit Virdi
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