DDC works over HDMI on linux? I switched to a displayport cable because I thought it wouldn't, and wanted to use ddcutil for setting brightness. I'll have to check that out. It might make the lack of CEC on PCs less annoying.
I've gotten CEC to work in Linux on my desktop computer. The funny thing is that most GPU HDMI ports don't implement CEC, but do implement CEC over DisplayPort. You simply need to find a DisplayPort to HDMI adapter that supports CEC.
