Re: usb_release_interface() + usb_close() -> broke communication

On Tue, Nov 09, 2004, Martin Vaillancourt <mvaillancourt <at> memoryexpertsinc.com> wrote:
> My 2 previous email seems too large!
> Now, I know exactly the cause of the problem, so I do a resume...
> 
> The Bulk Transaction with some data must toggle between the DATA PID
> DATA0 and DATA1. (Ref USB Specification 1.1 or 2.0)
> 
> So, when I Release the interface, do a usb_close, do a usb_open and
> re-claim the interface, the software resend by default the usb bulk
> command with the DATA0 even if the device is expecting it on the DATA1?
> 
> Question: Is there a flag somewhere in LibUSB that keep tracking of the
> DATA PID to used? 

libusb doesn't track anything to do with the data toggle. That is
handled by the kernel in all cases.

However, the SET_INTERFACE command is a control transaction that occurs
on the default control pipe. Data toggles rules are fixed for control
transfers, not to mention that the data toggle is per pipe.

I don't see how the SET_INTERFACE could interfere, unless the device
reset the data toggle when that occurs. I'll have to check the USB spec
to see what behavior the spec defines in this case.

JE

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