Any luck with sending DDC commands over HDMI?

#1

My “cooperative KVM switch” is based on a USB-only physical switch. The fact that my monitor has enough individual inputs, and udev rules that will send DDC commands over HDMI/DP from computer X to switch the monitor to computer X’s video input when the keyboard USB device is detected as having just been “plugged in” by the USB switch.

This has worked acceptably well with desktop, laptop and server Linux PCs, a Steam Deck on its dock, and even (with some horrible hacks) an Apple silicon MacBook.

For the Radxa Rock 5 ITX (running on the vendor kernel in the Armbian Ubuntu rolling releases) this doesn’t work though, as ddcutil doesn’t see DDC support on the relevant i2c address. Address 0x50 for monitor EDID info works, but address 0x37 (which seems to be the one needed for DDC) doesn’t show in ddcutil detect or i2cdetect output.

Has anyone had any luck with this? Is this issue rk3588-specific?

Thanks,

Juan.

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#2

It was my plan to use DDC but sadly I discovered that not all monitors support DDC… My newest, most expensive monitor cannot DDC. All other (much cheaper) were able to do it… I never tested it but good to know and good luck.