Turning LCD Backlight Off Using RPi4/Buster with dpms

[frankgould]

What I'm trying to do
I would like to configure my RPi4B:4GB desktop to shut off the monitor after a certain amount of time using xset dpms 300 300 300. Currently, the timeout blanks the screen but does not turn off power to the monitor, as it should. This was fixed for vcgencmd to turn off the monitor (link below). The same fix needs to be applied to dpms commands.

#1224

Description
When the dpms time expires, a blank screen is displayed but should be powered off.

To reproduce
Open a terminal window, type in xset dpms force off, notice the screen is still illuminated and not turned off.

Expected behaviour
The monitor shuts down using Energy Saver.

Actual behaviour
Screen blanks, blue monitor light remains illuminated, screen never turns off nor red light illuminated indicted monitor is powered off.

System
https://pastebin.com/PNnyw303

• Which model of Raspberry Pi: RPi4B
• Which OS and version:
  Raspberry Pi reference 2019-07-10
  Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 175dfb027ffabd4b8d5080097af0e51ed9a4a56c, stage5
• Which firmware version:
  Sep 30 2019 14:37:51
  Copyright (c) 2012 Broadcom
  version b1477501b8675de389acd184c2b7e7c4b2e39e4a (clean) (release) (start)
• Which kernel version:
  Linux FrankRaspi 4.19.75-v7l+ RPI3+ USB/NETBOOT does not start HDMI video #1271 SMP Mon Sep 30 13:51:15 BST 2019 armv7l GNU/Linux
  Graphics Driver: dtoverlay=vc4-fkms-v3d

[JamesH65]

I think this should also be fixed by raspberrypi/linux#3289

Please test and confirm (change currently in rpi-update)

[frankgould]

This appears to be working great on Buster. Thank you @JamesH65 !