2005/9/6, David Brownell <[EMAIL PROTECTED]>:
>
> > The first question is not specific to sl811 hcd: for periodic
> > transfer, does a urb must be resubmitted by the function driver after
> > its transfer completion is called or is it handled by the hcd/core ?
>
> There is no "automagic resubmit" in 2.6 kernels; drivers reissue URBs
> themselves, if that's what they want. (And they handle any errors
> themselves, rather than having usbcore or the hcd ignore them.)
>
but what happen if you get a NAK on a interrupt transaction ? Should
it be "automagically" rescheduled on the next period ? In general how
NAKed transactions are managed ? They seem to be retried forever
whatever the transfer type...Is it the hardware that is clever enough
to handle them ?
>
> > The second question is specific to sl811: periodic deschedules appear
> > in "finish_request" function. I don't understand the conditions needed
> > to start the periodic deschedule process. Does it happen when no more
> > transfer is pending for the current frame ?
>
> If the periodic endpoint in question has an empty transfer queue when the
> completion function returns, there's no point in leaving that endpoint in
> the schedule ... so it gets descheduled. After all, there'd be no point
> in leaving that part of the schedule reserved, if the driver stops using
> the slot which was temporarily reserved for it.
>
hmm, let say "sl811_urb_enqueue" is called with a periodic URB as
parameter. The function schedules the new periodic transfer and
reserved a bandwith for each frame where the transfer may occur (true
?). Then once the transfer is finished, "finish_request" is called.
This function calls "usb_hcd_giveback_urb" which can reschedulled the
interrupt transfer for the next period. But the first interrupt
transfer hasn't released its reserved bandwitdh and it won't until the
periodic endpoint has an empty transfer queue. Is it correct ?
Thanks.
--
Franck
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