Before any bulk endpoints are used, the userland-driver does
USBDeviceOpen(), GetNumberOfConfigurations(),
GetConfigurationDescriptorPtr(), SetConfiguration(),
CreateInterfaceInterface(), USBInterfaceOpen() and ResetPipes()
with a subsequent DeviceRequest() (with bRequest =
kUSBRqClearFeature and wValue = kUSBFeatureEndpointStall) to
synchronize the data-toggle.
Do you need to do the ResetPipe?
I've heard on some OSs you need to do this for reasons which are not
clear to me, as far as I know its not necessary on Mac OS.
On MacOS you need to do it for protocols like PTP (USB Still Imaging)
that use stalls for signalling.
I don't know if ClearPipeStallBothEnds() is smart about this or not,
but USBClearPipeStallByReference() won't set the toggle to zero on
the host end if it hasn't seen a stall on that pipe yet resulting in
data loss if you don't call USBResetPipeByReference().
PTP signals the host by stalling both the bulk in and out pipes --
the host sees one of the stalls first and tries to clear both --
because there hasn't been transaction on the other pipe yet,
USBClearPipeStallByReference() doesn't reset the toggle on the host
end causing a 50% chance of losing the next packet on that pipe.
It might be worth verifying that ClearPipeStallBothEnds() resets the
data toggle on the host side even if it doesn't thing the endpoint is
stalled or you may hit this case.
(Sorry, I implemented a PTP stack on 9, but not X)
Cheers,
-Steve
--
_________________________________________________________________________
Steve Sisak, CTO email@hidden
IOXperts, Inc. +1 617 876-2572
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