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kIOReturnIPCError
Look at the user-client boundary
kIOReturnIPCError is the common IOKit result for an error during IPC. It does not identify a bus-level transfer failure by itself. In a user-space IOKit call, a user client sits between the process and the kernel-side driver stack, so the request can fail while the method invocation, request marshalling, endpoint lifetime, or result delivery is being handled.
The code alone does not say which endpoint or stage failed. Treat it differently from kIOReturnIOError: first determine whether the operation ever reached the device-specific part of the stack. A removal, reset, terminated service, malformed request, or implementation-specific communication failure can require different recovery paths.
How to investigate
- Log the service identity, connection or interface lifecycle, method selector, and request/response sizes.
- Check for device removal, service termination, or process cleanup between opening the user client and issuing the call.
- Preserve both the IOKit result and any lower-level Mach or service diagnostics exposed by the API.
- Recreate a terminated connection only after rediscovering the current service object; do not reuse a stale handle.
References
- Apple XNU source: IOReturn.h
- Apple: IOKit architectural overview
- Apple: Introduction to IOKit Fundamentals
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