I generally call the user-space portion of a driver that's loaded into applications to be plugins and keep them outside of the umbrella of "drivers" but in this

I generally call the user-space portion of a driver that's loaded into applications to be plugins and keep them outside of the umbrella of "drivers" but in this case I think we both understand what's going on and are just disagreeing on what the terminology is. Given that the kext is essentially useless without the userspace component (and vice versa), I don't think it's unreasonable to call the plugin part of the driver. Note also that it's installed in /Library/Extensions. This certainly also matches the user experience: they download the NVIDIA "driver" installer which happens to install a bunch of kexts and also the user space components at the same time. These are plugins that implement AudioHardwarePlugIn, right? Correct. More generally, the IOCFPlugin mechanism, which paired user space components with kexts, is essentially dead for third-party driver developers thanks to the increasing lock-down of user space processes.