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kIOFireWireMultipleTalkers
One channel has one talker
FireWire isochronous traffic is sent on a numbered channel. Apple describes that channel as allowing one transmitting endpoint, called a talker, and any number of receiving endpoints, called listeners. kIOFireWireMultipleTalkers therefore identifies a stream-topology conflict: the requested setup would make more than one endpoint transmit on the same isochronous channel.
This is not an isochronous-bandwidth shortage. A channel can have sufficient reserved bandwidth and still be invalid because its sender role is already occupied. It also differs from kIOFireWireNoListenerOrTalker, which indicates that no stream endpoint has been attached, and from kIOFireWireChannelActive, which is a channel lifecycle-state conflict.
What to preserve in diagnostics
- Record the FireWire bus generation, channel number, and the direction of every local and remote isochronous port involved in the setup.
- Find the earlier transmitter reservation or stream object that still owns the talker role. Releasing a listener does not release a talker allocation.
- After a bus reset, revalidate the topology and recreate the intended channel setup through the owning API rather than assuming that stale application objects still describe the active bus generation.
- Do not try to address this status by requesting less bandwidth. The conflict is about transmitter ownership of one channel, not the quantity of bandwidth reserved for it.
References
- Apple: FireWire Device Interface Guide — isochronous channels, talkers, and listeners
- Apple: IOFireWireIsochPortInterface
- Linux kernel documentation: FireWire isochronous I/O and resource allocation
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