macOS kernel return 0xE0008020: meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A FireWire bus reset invalidated the generation associated with an in-flight command.

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kIOFireWireOutOfTLabels	kIOFireWireBogusDCLProgram

kIOFireWireBusReset

The command belongs to an earlier bus generation

kIOFireWireBusReset has a precise explanation in Apple's header: a bus reset occurred during command execution and the current bus generation no longer matches the generation specified in the command. This is a topology-consistency result, not an arbitrary I/O timeout.

After a reset, node IDs, root/bus-manager roles, and resource allocations can change. A command built with the previous generation may no longer target the same logical path, even when the same physical device is still connected. Recovery must revalidate the device and application state before a request is replayed.

Safe recovery boundary

Keep the request's original generation, target GUID and node ID, transaction type, and completion status.
Wait for the reset notification or callback that reports the new usable generation before submitting follow-up work.
Re-resolve the target and re-establish any resource allocation that the owning API does not preserve automatically.
Replay only idempotent operations or operations whose protocol confirms that the earlier command did not take effect.

References

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