@cullenp you asked "how do I access the CMIO extension in the first place"
From an app, use the routines in CoreMediaIO/CMIOHardwareObject.h to iterate through the CMIO objects, starting at kCMIOObjectSystemObject until you find an object with kCMIODevicePropertyDeviceUID with a value equal to the value of the deviceID parameter used in your initializer of your CMIOExtensionDevice.
You also asked "Is it possible to supply the Extension provider source with my queue? "
I'm not sure what you're asking here. You find the sink stream's ID by querying the sink device you found using the code above. Using that sink stream ID, you can copy its queue using CMIOStreamCopyBufferQueue, and you use CMSimpleQueueEnqueue to put your samples onto the sink stream's queue.
Topic:
App & System Services
SubTopic:
Drivers
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