I've watched the video of WWDC 2019 session 702, System Extensions and DriverKit, and I'm still a little puzzled.
For instance, what's the point of USBDriverKit, that is, why would I use it in preference to the already extant user-mode USB APIs? The demo shows an extension that does nothing - it logs to the debugger, but it doesn't provide any services to multiple clients in the system. In a KEXT, those services are provided by publishing them in the IORegistry; they provide well-known interfaces in the kernel to which a well-known user client can connect. If my extension ships in my own app, and provides services only to that app, I may as well implement the extension's functions directly in my app.
How does my app (or more importantly, a third-party app) communicate with my dext? That wasn't covered in session 702. Neither was the case of replacing or augmenting an existing system driver, for example filtering the data passing through a USB mass storage driver, based on sideband data which the standard system driver cannot convey. For a kext, I would simply call IORegisterService and the rest of the stack would be build on top of my driver.
Is the sample code for the demo of session 702 available? Any other sample code for DriverKit?
