macOS kernel return 0xE0004003: meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The host and endpoint are no longer synchronized on the USB data toggle.

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kIOUSBBitstufErr	kIOUSBPIDCheckErr

kIOUSBDataToggleErr

DATA0/DATA1 synchronization has been lost

kIOUSBDataToggleErr concerns the data-toggle state used to synchronize non-isochronous USB transfers. The host and endpoint maintain matching toggle state so that they can recognize an accepted packet and avoid treating a retransmission as new data. Apple's USB documentation notes that the sender advances after a positive acknowledgement and the receiver advances after it accepts an error-free packet with the expected identification.

This makes the code fundamentally different from kIOUSBCRCErr: CRC identifies a corrupted field; a data-toggle error identifies a state mismatch between the two sides of an endpoint. It also differs from a generic timeout, which says that completion was not observed in time but does not identify this synchronization state.

Recovery must match the endpoint state

Endpoint halts and data toggles are related. Apple documents that clearing a halt resets the toggle on the host side, while recovery that also needs to clear the endpoint's halt and reset its state must be performed explicitly or through the API intended for both ends. A host-only reset can therefore be insufficient when the device-side state also needs to change.

Log endpoint address, direction, transfer type, the last completed request, all cancels or aborts, and any reset, alternate-setting, configuration, or stall-recovery operation that preceded the failure.
Do not mix normal submissions with recovery on the same endpoint. Serialize the transition through an explicit draining and reinitialization state so callbacks cannot enqueue traffic against stale toggle state.
Account for every outstanding asynchronous request before reopening traffic. A higher-level command may have been accepted before synchronization was lost.
Use the device class specification to decide whether a command is safe to retry after endpoint recovery; the IOKit return value alone cannot establish command idempotence.

References

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