rpi-backlight not working in debian bullseye.

[pjmpessers]

rpi-backlight worked in debian buster, but not on bullseye. Installing gives this notification:

Defaulting to user installation because normal site-packages is not writeable Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple Collecting rpi-backlight Downloading https://www.piwheels.org/simple/rpi-backlight/rpi_backlight-2.4.1-py3-none-any.whl (9.8 kB) Installing collected packages: rpi-backlight Successfully installed rpi-backlight-2.4.1

After installation i gave the command:"echo 'SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/brightness /sys/class/backlight/%k/bl_power"' | sudo tee -a /etc/udev/rules.d/backlight-permissions.rules" and a reboot, when i give the command backlight -b5 it is saying it doesn't excist. With rpi-backlight -b5 it is saying:"

Traceback (most recent call last): File "/home/pi/.local/bin/rpi-backlight", line 8, in sys.exit(main()) File "/home/pi/.local/lib/python3.9/site-packages/rpi_backlight/cli.py", line 78, in main backlight = Backlight( File "/home/pi/.local/lib/python3.9/site-packages/rpi_backlight/init.py", line 75, in init self._max_brightness = self._get_value("max_brightness") # 255 File "/home/pi/.local/lib/python3.9/site-packages/rpi_backlight/init.py", line 92, in _get_value raise e File "/home/pi/.local/lib/python3.9/site-packages/rpi_backlight/init.py", line 84, in _get_value return int((self._backlight_sysfs_path / name).read_text()) File "/usr/lib/python3.9/pathlib.py", line 1255, in read_text with self.open(mode='r', encoding=encoding, errors=errors) as f: File "/usr/lib/python3.9/pathlib.py", line 1241, in open return io.open(self, mode, buffering, encoding, errors, newline, File "/usr/lib/python3.9/pathlib.py", line 1109, in _opener return self._accessor.open(self, flags, mode) FileNotFoundError: [Errno 2] No such file or directory: '/sys/class/backlight/rpi_backlight/max_brightness'

In /sys/class there is a directory "backlight", but no directory "rpi_backlight". Only a directory "10-0045" Has this to do with a new video-driver in the debian bullseye?

Thanks in advance.

[linusg]

I don't know. Try:

from rpi_backlight import Backlight
backlight = Backlight("/sys/class/backlight/10-0045")
backlight.brightness = 50

and see if that works.

[pjmpessers]

Thank you Linus.

This works great when i go into the python shell. But how can i make it work when i want to do the same with a SSH command? I want it to do the same with my home automation.

[linusg]

Glad to hear :)

If you mean using the rpi-backlight command, you can simply pass the path as the first argument:

rpi-backlight --options /sys/class/...

Out of curiosity, is this plain Debian or Raspbian / Raspberry Pi OS?

[pjmpessers]

With :"rpi-backlight --options /sys/class/backlight/..."

i got:

usage: rpi-backlight [-h] [--get-brightness] [-b VALUE] [--get-power] [-p VALUE] [-d DURATION] [-B {raspberry-pi,tinker-board,tinker-board-2}] [-V] [SYSFS_PATH] rpi-backlight: error: unrecognized arguments: --options

It is the Debian bullseye. I got no problem with the debian buster for my raspberry pi 4b

[linusg]

Sure, that was just an example - you need to provide some proper options ;)

If this was Raspbian I'd consider a built-in workaround, but for plain Debian I'm afraid the existing option of explicitly specifying a path will need to be sufficient enough.

[p1r473]

Running Bullseye on Raspbian (upgraded from Buster- not a fresh install) I have /sys/class/backlight/rpi_backlight/max_brightness

[pjmpessers]

Strange. I don't. I did a fresh install of the debian bullseye. And i can't create a /sys/class/backlight/rpi-backlight. It is saying "access denied" or something like that. And i'm not good at it, but don't know how to make a path.

[chris0z]

Yep have the same issue with a fresh installed Raspbian Buster 64-Bit its listed under /sys/class/10-0045 i've modified the init.py on my Pi manually. Line 29: BoardType.RASPBERRY_PI: "/sys/class/backlight/rpi_backlight/", to BoardType.RASPBERRY_PI: "/sys/class/10-0045/rpi_backlight/", its located in ~/.local/lib/python3.9/site-packages/rpi_backlight. Could be that you have another Python version then you have to change the version in the link

[Poli88]

I've got very similar issue, but I'm struggling with the last step you are suggesting. I'm running Raspbian bullseye 11 on Rpi4b and original 7" touch display. After installation, if I try to launch the GUI, I get the FileNotFoundError:

This is my sys/class directory content:

Running your solution on a command shell would lead to:

And now I'm stuck because it's not clear to me which commands are required to get the rpi-backlight folder up.

[linusg]

You're running that in a bash shell, but it's python code.

[Poli88]

Now I run it on python:

but the directory didn't change:

So I'm still having the same FileNotFoundError when trying to launch rpi-backlight-gui

Why the python commands are not effective ?