Hi Johannes,
> > > What's the difference between queuing URBs with the USB_QUEUE_BULK flag or
> > > with the next pointer?
> >
> > I think QUEUE_BULK is the only way to queue bulk URBs,
> > and the "next" pointer is only for scheduling rings of ISO urbs.
>
> "only" is incorrect. It can be used for any URB's.
Which "only"? That's the way OHCI behaves...
> The difference is performance. QUEUE_BULK on UHCI will setup the
> schedule to execute the next URB in the same frame. ->next requires a
> frame to pass.
That would seem to be an HCD-specific behavior. I couldn't quite
see how urb->next actually got used in "uhci.c"; it's tested, but not used.
In usb-uhci.c I see a uhci_submit_urb(next_urb) though ... is it possible
that the different HCDs handle iso rings differently?
> Strictly performance.
>
> Also, QUEUE_BULK is bulk only right now.
With a name like QUEUE_BULK, I'd call it a bug if it applied to any
other transfer type ... so, that "only" would correct.
- Dave
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