Johannes Erdfelt wrote:
>
> On Sun, Oct 13, 2002, David Brownell <[EMAIL PROTECTED]> wrote:
> >
> > >>The HC does not control bandwidth reclamation for low speed transfers. I
> > >>am not sure what happens in case of frame overrun (device stall, or
> > >>would that not matter in case of control endpoints?).
> > >
> > > Nothing that serious. The HC won't let a transfer spill over into the
> > > next frame. It'll just wait until the next frame and start the schedule
> > > over again.
> >
> > Does UHCI notice that while there's no time left for a lowspeed
> > transfer, there may be time for a high speed one ... and try
> > the high speed transfer?
>
> That's a good question. I don't recall seeing anything that describes
> that the UHCI will do that.
UHCI will simply initiate the low speed transfer, it does not check
whether it fits into the frame or not (The transfer will eventually stop
at the end of frame). And as it does not skip the low speed transfer it
cannot even see any pending high speed transfer. That is how I
understand the "spec", i.e. the UHCI design guide (or do you have access
to a more definite UHCI spec?), especially section 1.3:
<quote>
UHCI only allows for bandwidth reclamation of full speed control and
bulk transfers. The software must schedule low speed control transfers
such that they are guaranteed to complete within the current frame.
</quote>
Regards,
Stephan
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