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kIOReturnNotPermitted
Permission is not capability
kIOReturnNotPermitted means the operation is not allowed in the current context. The device may support the feature and be fully operational, but a policy, ownership rule, security check, state restriction, or protected mode prevents this caller from using it. This differs from kIOReturnUnsupported, where the operation itself is not implemented for the selected object or mode.
Blindly elevating privileges is not a general fix. The relevant restriction can belong to an IOKit user client, a kernel driver, an exclusive open owner, system policy, or a device state that must be changed through a different API. The diagnostic task is to identify the policy boundary that returned the status.
What to examine
- Record the client identity, entitlements or authorization context, and the exact user-client or interface method.
- Check whether another process owns the device exclusively before classifying the result as a privilege issue.
- Verify that the requested operation is valid in the current power, configuration, and media state.
- Use documented authorization and service interfaces instead of bypassing ownership checks through resets or forceful opens.
References
- Apple IOReturn.h reference
- Apple IOKit Fundamentals: Architectural Overview
- Apple USBInterfaceOpenSeize reference
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