> You build it directly into the GPU firmware and don't give the operating system any access to it.

State-level actors have been know to fiddle with firmware, specifically in the past for hard drives:

* https://www.sciencedirect.com/science/article/abs/pii/S13534...

* https://www.wired.com/2015/02/nsa-firmware-hacking/

I could see how cameras and microphones could be enticing targets.

That is still a blackbox code implementation which could be updated at any time. I trust wires, not programmers.

The firmware could be flashed to the device in factory and then write-protected by burning a fuse in the circuit.

This is not the case.

I mean, we don't really have any indication that the MacBook camera light is hard wired into anything.

For those who are interested, you can disassemble/image the assembly and see there is no funny business. People have done it. If there is something more complex than a power line, something is afoot.

I have no way of interrogating some GPU firmware.

I still don’t see how this could be more secure than connecting the LED to the camera’s power lines.