***Update WITH FIX to the libcec and i915 + DP++->HDMI cable with working cec-ctl behavior saga, posting for posterity:***
My suspicions were correct. To get libcec to be able to use the i915 ( core i5-7500 ) with the DP -> HDMI with tunneling working as a cec peripheral, you have to enable the Linux API ( for cec ) in the build.
Just throw the CEC_FRAMEWORK_SUPPORT="yes" value into the Generic project options file.
On the build, the Linux API is enabled in the libcec package build, and when using a build with that enabled, the /dev/cec0 produced by the i915 and a working DP->HDMI cable/adapter will be available as a CEC peripheral in settings out of the box.
Not sure why this isn't a default configuration for the Generic project though.
I do also have the same adapter as you have. I had to enter these commands on my Debian system, so that my Samsung TV is in HDMI-CEC (Anynet+) Mode. I'm directly working with Kodi.
apt install v4l-utils
cec-ctl --playback
cec-ctl -s --to 0 --active-source phys-addr=1.0.0.0The problem is, I always has to enter these commands everytime I boot my Dell Wyse 5070. Okay, that could be automated with .bashrc.
In Kodi | Settings | Interface there's no entry for CEC-Adapter. When I add it manually there's no possibility to configure it.
In LibreELEC the same steps would be necessary. I tried the official generic x86_x64 12.2 builds but nothing happens.
How did you manage to enter the CEC_FRAMEWORK_SUPPORT="yes" command? Do I have to build my own LibreELEC build or can I just enter this command into kernel command file? I don't unterstand your steps to get it working.
I also saw your other thread about enabling this behaviour as default in another thread.
Thank you for your explanations and thanks for investing so much developing time in this HDMI-CEC feature!