| Previous | Next |
| kIOFireWireNoChannels | kIOFireWireSeparateBus |
kIOFireWireChannelNotAvailable
Selected channel versus channel capacity
kIOFireWireChannelNotAvailable concerns the channel chosen for an isochronous setup. FireWire channels are shared bus resources, and a particular channel can be unavailable because it is already reserved or cannot be claimed in the current bus generation. The status does not by itself prove that the whole bus has exhausted every possible channel.
This distinction matters when an API can negotiate or select from a set of channels. kIOFireWireNoChannels is the broader resource-allocation failure; kIOFireWireChannelActive describes a lifecycle conflict with an existing active channel. Neither one should be diagnosed merely by counting visible FireWire devices, because the relevant state is the resource-manager allocation and the stream configuration.
How to narrow a channel collision
- Capture the exact requested or selected channel number, the candidate set if one was supplied, and the FireWire bus generation at the time of allocation.
- Determine whether the caller requested a fixed channel for protocol compatibility or whether another channel would be valid for the talker and listeners.
- Compare the allocation result before and after other isochronous streams are stopped. A change in result points to a resource collision, not to a malformed media payload.
- Do not reuse a channel handle or cached allocation result across a bus reset without validating it against the new generation and the current resource-manager state.
References
- Linux kernel documentation: channel bitmaps, IRM allocation, and bus-generation recovery
- IEEE 1394 technical introduction: isochronous resource management
- Apple: FireWire Device Interface Guide
Looking for a different code? Search another status or error code.