Toggle the display on and off via HDMI

[leograba]

Make it possible to switch the monitor off when there is no one around (at night or on weekends) and on whenever it makes sense (weekdays, work hours).

[leograba]

At first, https://github.com/Pulse-Eight/libcec looks like a good candidate. But then looking at the project maintenance history it seems dead.

The last release is from 2020 and since then only one PR was accepted, in 2022. Meanwhile, 142 issues and 18 PRs are open in the repo. No obvious fork has become the de facto main repository these days. The issues and PRs are quite recent though, so there may be hope.

But I also saw raspberrypi/bookworm-feedback#73 (comment) mentioning that these days it may be best to use cec-ctl from v4l-utils, which is actively and heavily maintained.

[leograba]

Resources to study:

• https://git.linuxtv.org/v4l-utils.git/
• https://manpages.debian.org/testing/v4l-utils/cec-ctl.1.en.html
• https://docs.kernel.org/admin-guide/media/cec.html

[leograba]

TIL that HDMI DDC and CEC are different things: https://hackaday.io/project/166764-hdmi-ddc-cec-converter