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kIOUSBLowLatencyBufferNotPreviouslyAllocated
The payload buffer is not valid for this submission path
kIOUSBLowLatencyBufferNotPreviouslyAllocated identifies the data-buffer half of a low-latency isochronous request. IOUSBFamily did not find a prior preparation for the payload memory supplied to the request. This differs from kIOUSBLowLatencyFrameListNotPreviouslyAllocated: the latter concerns per-frame status records, while this code concerns the audio, video, or other payload bytes themselves.
Changing packet size, frame count, or callback logic cannot repair an unprepared buffer. The required setup must occur before the request is submitted, and the same prepared allocation must remain valid until the asynchronous completion path has finished using it.
Diagnostic checklist
- Identify the exact payload pointer, length, direction, endpoint, and low-latency buffer-preparation call used for this request.
- Check that the request did not switch to a different allocation after preparation, including a resized buffer, copied wrapper, or temporary object.
- Keep data-buffer and frame-list ownership separate in logs and cleanup code; one being prepared does not prove the other is prepared.
- On reconfiguration, cancellation, or device removal, retire old prepared buffers before reopening the interface and preparing replacements.
References
- Apple: IOUSBFamily error codes
- Apple: low-latency isochronous completion
- IOKit SDK header: low-latency USB buffer interfaces
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