Ubuntu: I can't lower the backlight/brightness



Question:

Why I can't control the brightness/backlight level?

At the first:

Notebook Positivo BGH - C500 Series.   Processor: AMD C60 series (dual core 800 mhz-1ghz)  GPU: Radeon HD 6290 (worked with fglrx/Catalyst)  

Hello everybody, this is my first post in 8-years-use of Ubuntu/Kubuntu, I've never had problems with any version, but when I've upgraded from Willy to Xenial I haven't take care in the latest version that the AMD/ATI property drivers (fglrx) have been discontinued or unsupported by the developers, and they advice against not upgrade for AMD users. The Fn keys dosen't work!

However, after upgrade, when I was configuring, I want install drivers from console:

sudo apt-get install fglrx fglrx-updates   "fglrx" and "fglrx-updates" has no candidates  

In the version Willy (and previous versions), I can't control or lower the brightness/backlight util the property drivers have been instaled.

In Ubuntu 16.04, the drivers are:

xserver-xorg-video-amdgpu  xserver-xorg-video-radeon  

And These are open drivers, but this is not the trouble really.

I've tried the following procedures:

I tried to put various links, but the newbies can't post more 2 links

Abstract:

1. Can't change backlight level by installing driver.

    sudo apt-get install xserver-org-video-amdgpu      sudo apt-get install xserver-org-video-radeon  

##2. It persist high shine, despite modifing /sys/class/backlight, and the promp shows me (radeon_bl0 is present):

    lspci | grep ati      00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Wrestler [Radeon HD 6290]      ls /sys/class/backlight      radeon_bl0  

Inside the folder, brightness, max_brightness, actual_brightness, bl_power and others are present

    echo > 10 /sys/class/backlight/radeon_bl0/brightness   

There is no effect

    echo > 100 /sys/class/backlight/radeon_bl0/max_brightness      permission denied      chmod 0777 /sys/class/backlight/radeon_bl0/max_brightness      nano /sys/class/backlight/radeon_bl0/max_brighness      modifing 255 to 100      Ctrl+O > I/O Error       chmod 0777 /sys/class/backlight      The same result >  I/O Error   

And find another way:

    ls -alh /sys/class/backlight      lrwxrwxrwx  1 root root 0 abr 23 12:23 radeon_bl0 -> ../../devices/pci0000:00/0000:00:01.0/drm/card0/card0-LVDS-1/radeon_bl0  

And trying the same, and no effect.

3. Modifing the grub:

    GRUB_CMDLINE_LINUX="acpi_osi=Linux" | No effect      GRUB_CMDLINE_LINUX="acpi_backlight=none" | No effect      GRUB_CMDLINE_LINUX="acpi_backlight=vendor" | No effect      GRUB_CMDLINE_LINUX="acpi_backlight=video" | No effect      GRUB_CMDLINE_LINUX="acpi_backlight0" | No effect      GRUB_CMDLINE_LINUX="acpi_backlight=radeon_bl0" | No effect  

Rebooting and edit grub (with the same sentences) before start Ubuntu, strangely It don't start. Starting in "recovery mode", /sys/class/backlight, shows me:

     acpi_video0  

But the SDDM dosen't start.

4. Adding the X11 configuration.

      cd /usr/share/X11/xorg.conf.d        dir > 10-amdgpu.conf is present        nano 10-amdgpu.conf | shows me                   Section "OutputClass"                   Identifier "AMDgpu"                   MatchDriver "amdgpu"                   Driver "amdgpu"                 EndSection  I added                  Section "Device"                  Identifier "card0" | put also "AMDgpu"                  Driver "amdgpu"                   Option "Backlight" "radeon_bl0"                  BusID "PCI:00:01:01"               End Section  

But it dosen't work, due option "Backlight" is for intel driver. I revised man of amdgpu and not figure this option. In several times, neither starts SDDM.

5. Using the command setpci:

     setpci -s 00:01.0 F4.B=7F | Not work       setpci -s 00:01.0 F4.B=FF | Not work       setpci -s 00:01.0 F4.B=50 | Not work       setpci -s 00:01.0 F4.B=80 | Not work  

This video card not support by the setpci

6. Installing xbacklight

     sudo apt-get install xbacklight       xbacklight -s 80 | there is no effect        No outputs have backlight property        xbacklight -d LVDS -s 80       RANDR Query Version returned error -1  

It dosen't work, I've searched, and xbacklight is deprecated for xf86-video-ati for control of backlight, I've installed script "light" (lightscript) but It dosen't work too.

7. Making udev rule:

          nano /etc/udev/rules.d/81-backlight.rules              # Set backlight level to 8           SUBSYSTEM=="backlight", ACTION=="add", KERNEL=="acpi_video0", ATTR{brightness}="8"            Save & Exit and there is no effect after boot  

8. Using systemd-backlight service.

           I don't understeand how this works, but I've got this from the prompt:              systemctl list-units | grep -i backl               systemd-backlight@backlight:radeon_bl0.service     loaded active exited    Load/Save Screen Backlight Brightness of backlight:radeon_bl0               system-systemd\x2dbacklight.slice       loaded active active    system-systemd\x2dbacklight.slice  

The systemd-backlight service is loaded for /sys/class/backlight ! But It dosen't work, the backlight don't change.

9. Using xrandr

       Finally I put in the console:  xrandr --output LVDS-1 --brightness 0.6 | 0.4 | 0.3  Previously identified output   

This "worked" for me, but when I restart the values of xrandr going to default, by more than I put xrandr --output LVDS1 --brightness 0.5 at start session. (On Kde by the System Settings>Start and Shutdown)

Conclussion

In all cases, the brightness/backlight ever is high, it dosen't matter I do, the Fn Keys don't work, and the Kde Indicator for brightness goes to 0 and the LCD looks the Christmas tree because it's turn up/down infinitely.

Anyone have more ideas?

Sorry for my bad english!


Solution:1

There's something very odd about the syntax you're using to write to the files in /sys/class/backlight/. Please try this, instead:

echo 128 | sudo tee /sys/class/backlight/radeon_bl0/brightness  

By the way, you were not able to modify "max_brightness" because that file is just there to let you know the maximum brightness you can use. You need to change the file named "brightness".

About your shell syntax: The shell redirection operator > only works if you're already running a shell as root (for example, using sudo -s), but I should let you know that doing so is generally considered a bad idea. Logging in to a root shell gives you great power; and with great power comes great whopping mistakes. It's easy to forget you're running as root and then accidentally mess up your whole system. That's why I recommend sudo, as in the example above. Sudo is a reminder to be careful: anything after the word sudo is normally off-limits and potentially dangerous.

However, if you are curious, it is possible to use the > file redirection operator the way you were asking, but you'd need to change the arguments around. The part that comes after the > is the filename to write to, the part before it is the command whose output you want to redirect. So, for example,

$ sudo -s  # cd /sys/class/backlight/*/  # echo 128  128  # echo 100 > brightness  # cat brightness  100  # echo 200 > brightness  # cat max_brightness  255  # cat max_brightness > brightness  # cat brightness  255  # exit  $   

(You'll notice your prompt changes to a hash mark when you're running a root shell. That's a subtle warning sign. Typing exit will get you back to the safety of your normal user account.)


Solution:2

there is no standard brightness level resolution in universal implementation. For example one of my linux boxes is a Toshiba Satellite L510 and has an 8 bit resolution. i.e. my /sys/class/backlight/acpi_video0/brightnesswill only accept values in [0,7]. I also have seen one other system has a resolution of 23 bits. i.e. [0-22].

To know the range of brightness values, read your /sys/class/backlight/radeon_bl0/max_brightness file. Also the value of the max_brightness file is most likely set by your system's firmware and you can not write to it. But the /sys/class/backlight/radeon_bl0/brightness file can be written to as long as the value being written is between 0 and the result of

cat /sys/class/backlight/radeon_bl0/max_brightness

also suspending your system and waking it up usually fixes some problems with regard to ACPI and UEFI - by extension functions keys. to suspend your system use the following command.

sudo pm-suspend

then wake your system by pressing the power button and check is the function keys are working.


Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
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