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kIOReturnNotResponding
What the failure suggests
kIOReturnNotResponding indicates that the target did not answer as required by the operation. It is stronger than “not ready”: the operation got far enough to expect a response but could not obtain one. A cable, hub, power state, device firmware, controller reset, stalled transport, or a driver-side communication path can all produce the same high-level status.
Because IOKit return values are family-neutral, do not assume that this code proves a hardware defect. The important evidence is the first failed transaction and the state immediately before it. A later kIOReturnNoDevice after a reset, for example, can be part of the same incident but requires different cleanup.
What to collect
- Log the specific command or transfer, timeout, endpoint or media operation, and whether earlier operations succeeded.
- Inspect system logs and I/O Registry state for reset, detach, power, or reconfiguration events.
- For USB, retain a bus trace when possible; protocol-level evidence separates an unresponsive endpoint from host-side cancellation.
- Close and rediscover the device after a confirmed reset or removal instead of continuing through a possibly invalid interface.
References
- Apple IOReturn.h reference
- Apple: Working With USB Device Interfaces
- USB-IF: USB 2.0 Specification
- libusb device lifecycle and interface claims
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