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kIOUSBNoAsyncPortErr
Asynchronous delivery could not be established
kIOUSBNoAsyncPortErr identifies a missing asynchronous port in the legacy IOUSBFamily interface. It does not say that a USB device endpoint rejected a transfer. Instead, the host-side mechanism required to deliver asynchronous completion or callback activity was unavailable for the request.
That makes callback lifecycle central to the diagnosis. A process can have a valid device and interface reference yet fail to establish the asynchronous path because it used the wrong API generation, released the associated object too early, or attempted to reuse state after a disconnect or reset.
Keep the asynchronous context visible
- Log which API object created the asynchronous path, the run-loop or dispatch context, and the lifetime of the owning interface reference.
- Verify that the code uses the API's asynchronous setup sequence before submitting asynchronous transfers.
- Correlate the status with process teardown, device removal, sleep/wake, and controller reset events.
- Do not replace asynchronous calls with blocking calls as a blanket workaround; first determine whether the caller needs ordered completion and cancellation semantics.
References
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