I always assumed that it was a separate i2c bus per HDMI link and that it was the AVR’s job to handle a request from something and send the right requests to everything else.
Much like i2c, any message put on the bus is transmitted to everything on the bus.
Version 1.0 and later of the HDMI spec even mandate that you have to connect those pins across all HDMI ports on your device even if you don't do anything with them.
Okay, now I’m curious. If the pins are just connected across all ports, how does the AVR tell which CEC-speaking device is on which port? Chip select or similar pins?
