Pi4 hdmi_blanking

In the config.txt (Raspberry Pi) documentation, it states that hdmi_blanking isn’t supported on the Pi 4. It works here so I think this might need updating.
(Came across it trying to find why my BB -xM would blank but not the PI on the same monitor)

Yes it works on the Pi4 with RISC OS, but not under Rasbian!

In the config.txt (Raspberry Pi) documentation, it states that hdmi_blanking isn’t supported on the Pi 4. It works here so I think this might need updating.

Well spotted that man. Revised config.txt wiki page now online.

In my defence, the official Raspberry Pi documentation does still state that the feature has not been implemented. That is presumably because it doesn’t work with Raspbian, as Druck has pointed out.

Maybe someone could help out the poor Raspbian folks, and point them at some working code from RISC OS?

I have to remember to set my HDMI switch to my RISC OS Pi4 rather than my Linux one, or the monitor backlight stays on all night.

Yes it works on the Pi4 with RISC OS, but not under Rasbian!

Raspberry Pi OS does put the monitor fully to sleep here on both the RPi4 and RPi400. IIRC putting the monitor into a low power state rather than just outputting black level was added to the firmware in late 2019.

Raspberry Pi OS does put the monitor fully to sleep here on both the RPi4 and RPi400.

Though blanking does work fully on the RPi4 and RPi400 is does not do that by writing hdmi_blanking=1 into config.txt, so how it does it is a minor mystery right now.

Blanking is enabled/disabled in Preferences > Raspberry Pi Configuration > Display or from the terminal with sudo raspi-config > Display Options.

@David I don’t know how you’ve managed it, as all raspi-config does for me is set hdmi_blanking=1. I’ve tried all sorts of X settings, and installed the X-Screensaver to no avail.

@David I don’t know how you’ve managed it, as all raspi-config does for me is set hdmi_blanking=1.

I don’t know either! It just works!

The installations are all recent, eg :-

pi@raspberry64GB:~ $ vcgencmd bootloader_version
Apr 29 2021 17:11:25

pi@raspberry64GB:~ $ vcgencmd version
May 27 2021 14:02:15 

pi@raspberry64GB:~ $ 

This from config.txt may, or may not, have something to do with it :-

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

edit Or perhaps not, hdmi_blanking does nor appear in config.txt on the RPi3B+ either.

This is the best explanation I have found so far, but it may be old.

When the RPi4 first turned up here with RISC OS the monitor only blanked itself, the backlight remained on.

I rather think the official Raspberry Pi document is correct, specifically for hdmi_blanking, on the RPi4, but fortunately RISC OS hasn’t read it.