What does macOS kernel return 0xE000404F (kIOUSBPipeStalled) mean?

 
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kIOUSBPipeStalled

A stall belongs to the endpoint, not necessarily the whole device

kIOUSBPipeStalled reports that the requested pipe is halted. A stall is different from a timeout: it is a defined endpoint condition, and another transfer on the same pipe is not a valid recovery strategy by itself. Other interfaces and endpoints on the device can remain usable, so diagnosing only the device name is usually too coarse.

Apple's USB documentation distinguishes controller-side pipe clearing from restoring the device endpoint state. A correct recovery may need a protocol-specific control request, data-toggle resynchronization, and explicit handling of requests that were outstanding when the halt was noticed. The safe sequence depends on the transfer type and device class.

Before resubmitting work

  • Capture the endpoint address, transfer type, direction, command or protocol operation, and all queued request identifiers.
  • Determine whether the device protocol defines a required recovery command in addition to host-side pipe clearing.
  • Account for returned or cancelled asynchronous requests and verify data-toggle handling before reopening normal traffic.
  • Do not replay a non-idempotent command until the device protocol confirms whether it was accepted before the stall.

References

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