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kIOFWMessagePowerStateChanged
kIOFWMessagePowerStateChanged reports a FireWire power-state transition. The transition can invalidate assumptions about device availability, bus generation, and pending operations, so correlate it with the sleep/wake and provider event sequence.
Read the status in context
IOKit return values, internal tokens, and service messages share an integer representation but not the same control-flow meaning. Determine whether the API returns the value or delivers it as a message before treating it as failure.
Diagnostic facts
| Capture | Diagnostic value |
|---|---|
| Old/new power state, device registry path, bus generation, sleep/wake timeline, and pending transactions. | Identifies the concrete object and operation associated with FireWire power-state-change message. |
| Numeric IOReturn/message value decoded with the matching SDK header. | Separates argument or lifecycle state from the provider beneath kIOFWMessagePowerStateChanged. |
| Registry generation and first provider/client event before the result. | Correlates the message with the registry generation and provider event that preceded the power transition. |
| Known-good device or service state on the same macOS/driver build. | Shows whether kIOFWMessagePowerStateChanged is the first result or a translated summary. |
Verification path
- Suspend and resume a controlled device while tracing message order.
- Change one topology or lifecycle condition while keeping the request payload fixed.
- Verify cleanup and object lifetime after the controlled operation.
Closing the incident
Targeted correction. Pause submissions, rebuild state required after wake, and revalidate device generation before resuming.
Acceptance criterion. Sleep/wake cycles preserve data integrity and pending work is canceled or resumed by explicit policy.
Technical references
- Apple XNU: IOReturn definitions — defines the status namespace used.
- Apple: IOKit documentation — documents the API or lifecycle boundary behind it.
- Apple OSS: XNU source — provides ABI, implementation, or protocol context.
- Apple XNU: FireWire family common definitions — supports the portability and verification limits.
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