Question: How to use dtparam=hdmi option

[Akkiesoft]

Hi.

I noticed that HDMI can be disabled with the dtparam=hdmi option.

https://github.com/raspberrypi/linux/pull/5181

So I wrote following lines into /boot/config.txt then reboot Pi.

Code: Select all

dtparam=hdmi=off
# Pi4?
dtparam=hdmi0=off
dtparam=hdmi1=off

However, these options are not working and do not appear to be able to turn off HDMI.

I was expecting HDMI with the dtparam option, just as I could turn it off with tvservice -o when using fkms, is that not the case?

I tested with Raspberry Pi OS (32-bit) kernel 5.15.84-v7+ and 6.1.21-v8+, on Pi3B+ and Pi4.

[Akkiesoft]

I forgot to write my purpose: I want to save power by disabling HDMI.

I saw this post.
viewtopic.php?p=2084904#p2084904

I tried this command and it seems to have saved about 100mA of power.

Code: Select all

$ DISPLAY=:0.0 xrandr --output HDMI-1 --off

Am I correct in understanding that xrandr is an alternative to tvservice -o/-p for power saving?
But then what is dtparam for?