Re: [Linux-usb-users] USB: Non zero status

On Fri, 17 Aug 2007, Martin Bachem wrote:

> Hi!
> I followed the thread regarding the -EXDEV error, which leads me to the
> same point.

Which thread is that?  You have to be much more specific; I read many
of threads every day.

> I'm running an ISDN USB device, which is running ISO 6 endpoints. Each
> Endpoint (3 tx + 3 rx) is handled by two ISO URBs, each ISO URB is
> contain 8 ISO packets, each ISO packet is containing 1 up to 8 bytes
> payload. I use two ISO URBs for each endpoints to have a seamless ISO
> traffic, which is essential for my flow-control.
> 
> >From time to time I get the -EXDEV error in the ISO completion.

Which host controller driver do you use?  uhci-hcd?

> rx_iso_complete with -EXDEV urb->status -18, fifonum 5
> rx_iso_complete ISO packet 1, status: -18
> rx_iso_complete ISO packet 2, status: -18
> rx_iso_complete ISO packet 3, status: -18
...
> tx_iso_complete with -EXDEV, urb->status -18, fifonum 4
> tx_iso_complete with -EXDEV, ISO packet 1, status: -18
> tx_iso_complete with -EXDEV, ISO packet 2, status: -18
> tx_iso_complete with -EXDEV, ISO packet 3, status: -18
...
> 
> That means 6 ISO URBs get a callback with the 'partially completed'
> error, each one with packet 1 to 3.
> 
> Is the recommended handling of -EXDEV not to handle it at all, but go on
> re submitting URBs?

There is no special recommendation; you should do whatever is
appropriate in your situation.  You might be able to avoid the errors
by using more packets per URB.

>  Should I assume the data contained in the first 3 of
> 8 ISO packets within that URBs was lost?

Yes.  Whenever the packet's status is not 0 you should assume the data 
was lost.

Alan Stern


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