How does one get the list of controls which a CMIOObject has to offer? How do the objects in the CMIO hierarchy map to CMIOExtension objects?
I expected the hierarchy to be something like this:
the system has owned objects of type:
'aplg' `(kCMIOPlugInClassID)` has owned objects of type
'adev' `(kCMIODeviceClassID,` which may have owned objects of type
'actl' `(kCMIOControlClassID)` and has at least one owned object of type
'astr' `(kCMIOStreamClassID),` each of which may have owned objects of type
'actl' `(kCMIOControlClassID)`
Instead, when I recursively traverse the object hierarchy, I find the devices and the plug-ins at the same level (under the system object). Only some of the device in my system have owned streams, although they all have a kCMIODevicePropertyStreams ('stm#') property.
None of the devices or streams appear to have any controls, and none of the streams have any owned objects. I'm not using the qualifier when searching for owned objects, because the documentation implies that it may be nil if I'm not interested in narrowing my search.
Should I expect to find any devices or streams with controls? And if so, how do I get a list of them? CMIOHardwareObject.h says that "Wildcards... are especially useful ...for querying an CMIOObject's list of CMIOControls. ", but there's no example of how to do this.
My own device (from my camera extension) has no owned objects of type stream. I don't see any API call to convey ownership of the stream I create by the device it belongs to. How does the OS decide that a stream is 'owned' by a device?
I've tried various scopes and elements - kCMIOObjectPropertyScopeGlobal, kCMIOObjectPropertyScopeWildcard, kCMIOControlPropertyScope, and kCMIOObjectPropertyElementMain, kCMIOObjectPropertyElementWildcard and kCMIOControlPropertyElement. I can't get a list of controls using any of these.
Ultimately, I'm trying to find my provider, my devices and my streams using the CMIO interface, so that I can set and query properties on them. Is it reasonable to assume that the CMIOObject of type 'aplg' is the one corresponding to a CMIOExtensionProviderSource?
This is on Ventura 13.4.1 on M1.