Re: Question regarding short transfers

On Tuesday 22 May 2007, Alan Stern wrote:
> On Tue, 22 May 2007, David Brownell wrote:
> 
> > > > 2) What happens if the device terminates the transfer during the 4KB
> > > > (after say 3700 bytes received, with a short packet)?  
> > > > 
> > > > Thus:
> > > > urb->transfer_buffer_length = 4096
> > > > urb->actual_length          = 3700
> > > > 
> > > > I believe that the HC driver should do the following test:
> > > > 
> > > > if( (urb->actual_length < urb->transfer_buffer_length) &&
> > > > 	(urb->transfer_flags & URB_SHORT_NOT_OK) )
> > > >  	urb->status = -EREMOTEIO;
> > > > 
> > > > So if URB_SHORT_NOT_OK is set then -EREMOTEIO will be returned And if
> > > > URB_SHORT_NOT_OK is not set the 0 will be returned.
> > > > 
> > > > Is this correct ?
> > > 
> > > Yes.  The same thing would happen to the 8K URB in your first question.
> > > 
> > > > Again I assume that the 8K urb should be completed immediately ?
> > > > If so with what status ?
> > > 
> > > No.  The 4K URB's completion handler would see the -EREMOTEIO error and 
> > 
> > TYPO -- 8K, not 4K ...
> 
> Look again -- the question assumes that the first 4K URB comes up short
> and then asks what would happen to the 8K URB.

Sorry, you're right.  I was thinking this was an extension
of question #1...

In patent-ese, #2 was independent, not dependent.  ;)


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