Re: Help with debugging no-callback problem with IrDA USB dongle

On Wed, 2 May 2007, [UTF-8] Alex Villací­s Lasso wrote:

> >> submit the interrupt urbs for either endpoint in the driver code, my callback
> >> code never gets called at all - not even to signal an error while
> >> submitting the
> >> urb.
> >>     
> >
> > That never happens.  The callback routine is invoked when the URB
> > completes, and if the submission failed then the URB wasn't accepted so of
> > course it can never complete.
> >
> >   
> Hmm... I was under the impression that if usb_submit_urb() returned 0, 
> then the callback routine would eventually get called, either because it 
> completed,

That much is right.

> or because an error occurred in submission - such as a timeout.

No.  If usb_submit_urb() returned 0 then by definition an error did not 
occur in submission.  A timeout isn't a submission error, and in fact the 
URB-handling parts of the USB stack don't have any timeouts.


> > Apparently your driver doesn't send anything to the device when it is 
> > probed.
> >
> >   
> The stir4200 driver also doesn't do anything to the device, other than 
> usb_reset_configuration(). What kind of operation might be necessary to 
> do at the probe function?

How should I know?  It depends entirely on the device.

On the other hand, I doubt that the usb_reset_configuration() call is 
needed.  It merely duplicates what the USB core did a few moments earlier.

> > Why does your driver bother to do a Clear-Halt?  It should not be needed.
> >
> >   
> Again, because stir4200 does it and I was taking it as one of the models 
> for writing my driver. I thought this was a required part of the setup. 
> I will try removing it at home and see if it makes any difference.

It almost certainly is not required.

> > Like Oliver said, you probably need to do some sort of initialization of 
> > the device before it will start working.
> >
> > Alan Stern
> >
> >   
> Maybe, but I could not find any evidence of such an initialization 
> sequence in the SnoopyPro dump done under Windows XP (attached). I 
> deduced that no initialization sequence was needed. So, I am not looking 
> hard enough, or SnoopyPro is buggy / hides information from me.

I don't see anything special in the log either.  Maybe the device simply 
doesn't like your Clear-Halt requests.

Alan Stern


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