Re: code review request: simple usb stream interface (susi)

On Thu, 8 Feb 2007, Edwin Olson wrote:

> > So I see.  Do you happen to have the URB_NO_FSBR flag turned on in your
> > URBs? 
> Not in my code, at least... What does it do?

It does pretty much what you said you saw -- it hints to the controller
driver that this URB doesn't need more than one packet per frame.

> >  Have you tried using a USB bus analyzer to find out what's really 
> > happening?
> I wish I had one!

I have one.  If you actually are at MIT you could come visit me.  My
office is just down the road, within walking distance.

> More testing seems to indicate that multiple outstanding URBs does make 
> a very small (10%?) difference in performance, and staring at usbmon, it 
> appears that sometimes I do in fact get multiple callbacks from the same 
> frame. But it's quite rare...

Bus analysis is the way to go.

Alan Stern


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