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kIOReturnNoPower
Power is part of the device lifecycle
kIOReturnNoPower indicates that the device lacks the power state required for the operation. It can appear around sleep and wake, a bus power transition, a suspended peripheral, a disabled port, or a device whose power budget is not available. The error is not synonymous with a missing device: the system may still enumerate and describe the hardware while refusing I/O until power is restored.
Repeatedly reopening the interface does not itself supply power. Recovery should follow the owner of the power transition—system power management, a hub or controller, a device-specific policy, or the user. Once the device reappears in a usable state, validate configuration again because some buses reset configuration after a power event.
Practical checks
- Correlate the first error with sleep, wake, USB suspend, port power, or battery/power-management events.
- Inspect whether other functions on the same hub or controller also changed state.
- Use notification-driven reinitialization after wake rather than assuming pre-sleep handles remain ready.
- For externally powered devices, verify the physical power path before treating this solely as a software permission issue.
References
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