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#1 2021-03-03 18:20:55

gavsiu
Member
Registered: 2016-04-08
Posts: 20

Lenovo Legion 7i backlight does not "work out of the box"

The wiki claims the Legion 7i has a working backlight out of the box, but not for me.

/sys/class/backlight/intel_backlight does exist, but does nothing. The backlight either goes 100% or 0%. There is no in between. The brightness file is being written to. I've tried all the kernel command line options from Backlight wiki, Intel wiki and pretty much anything else I've found online. I've even tried changing the nvidia card, but that shouldn't have worked anyway because it's not the default card. I went through all the troubleshooting steps on both the Backlight and Intel wiki.

The only workaround is using xrandr brightness, but that is not the ideal way. It also prevents me from calibrating the screen as displaycal sets the xrandr brightness to 1.0 (100%).

I'd love to see how whoever said it works out of the box did it.

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#2 2021-03-05 14:04:23

adigitoleo
Member
From: Australia
Registered: 2020-08-02
Posts: 32

Re: Lenovo Legion 7i backlight does not "work out of the box"

I'm no expert, but another thing to check could be the driver. Are you using proprietary or noveau?

Seems like there were some issues with recent nvidia drivers, e.g.

https://forum.manjaro.org/t/cant-adjust … xfce/28771

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#3 2021-03-05 19:51:09

gavsiu
Member
Registered: 2016-04-08
Posts: 20

Re: Lenovo Legion 7i backlight does not "work out of the box"

I tried everything from that thread. I am using proprietary drivers. That thread seems to only talk about different Linux kernels being part of the issue.

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#4 2021-03-06 01:49:25

adigitoleo
Member
From: Australia
Registered: 2020-08-02
Posts: 32

Re: Lenovo Legion 7i backlight does not "work out of the box"

Hmm, you have dual graphics? As in one dedicated nvidia card and one integrated intel card?

If yes, can you change between "discrete" and "switchable" modes (something like that) in the BIOS?

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#5 2021-03-06 02:27:50

RDDO
Member
From: Brazil
Registered: 2008-02-21
Posts: 21

Re: Lenovo Legion 7i backlight does not "work out of the box"

for the legion 5 (radeon/nvidia 1660 Ti) just installed acpilight and added the 90-backlight.rules file to /etc/udev... as explained in the package github page. I have also added these lines to /etc/X11/xorg.conf

Section "Device"
[...]
BusID       "PCI:1:0:0"
Option      "RegistryDwords" "EnableBrightnessControl=1" 
EndSection

I'm using the latest nvidia driver and running the discrete graphics only (set at BIOS). After all was set, tried running at terminal

xbacklight -ctrl nvidia_0 -inc 10

if it works, a basic shell script to increase/decrease the bightness bound to a key seals the deal.

I'm using the discrete graphics because I still can't get the switchable gpus to work, read the PRIME, Optimus and other bunch, but still didn't understood how it works. I'm also having trouble with scalling, everything seems like 125% (small sized) any tips would be appreciated.

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#6 2021-03-06 17:29:32

gavsiu
Member
Registered: 2016-04-08
Posts: 20

Re: Lenovo Legion 7i backlight does not "work out of the box"

I have dual graphics, but I've kept it in hybrid mode. If I have to use discrete graphics to get backlight to work, I'd rather have a non-working backlight and use xrandr brightness.

Correct me if I'm wrong, but I think it will probably use more battery running the discrete GPU all the time than backlight at 100%. If it was like my old laptop with a dead battery, I'd run the discrete GPU on A/C.

At the moment, I am using oled-linux and xorg-xbacklight to have working brightness controls.

I have tried adding the RegistryDwords option and has done nothing.

To get switchable GPUs to work, I kept the BIOS in hybrid mode. I installed proprietary NVIDIA drivers. It should boot using Intel GPU.

glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Mesa Intel(R) UHD Graphics (CML GT2)

I only use the NVIDIA GPU for Steam, but you could launch any app using the same method. All my Steam games have this at the end of the launch options:

prime-run %command%

You could test it or run any other app by running it in terminal:

prime-run glxinfo | grep "OpenGL renderer"

I guess you could add it to the desktop files if you use menus so you don't have to launch from a terminal.

In the end, I do really want an actual working backlight for battery efficiency. I had a 7 year old 17" laptop with a dead battery for years. It was a brick before the battery died and had poor battery life. Then it became a permanent desktop. The Legion 7i actually seems to have a pretty decent battery life for a gaming laptop even with the backlight at 100%.

Also without a working backlight, I cannot color calibrate my screen. Because I'm using xrandr brightness, displaycal sets it back at 100%.

Last edited by gavsiu (2021-03-06 17:41:51)

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#7 2021-03-07 01:28:38

adigitoleo
Member
From: Australia
Registered: 2020-08-02
Posts: 32

Re: Lenovo Legion 7i backlight does not "work out of the box"

You're right, and there should be a way to get brightness to work in hybrid mode. You said the value of

/sys/class/backlight/intel_backlight/brightness

is being changed, but nothing happens, right? You've probably tried xbacklight already (no luck?) and manually writing to the file like

sudo echo N > /sys/class/backlight/intel_backlight/brightness

where N is lower than the current value, could be worth a try. In case xbacklight works, make sure you've tried:

https://wiki.archlinux.org/index.php/Ba … ess_change

I'm not really familiar with dual graphics, so hopefully someone more knowledgable can offer better advice.

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#8 2021-03-10 17:58:34

gavsiu
Member
Registered: 2016-04-08
Posts: 20

Re: Lenovo Legion 7i backlight does not "work out of the box"

adigitoleo wrote:

You're right, and there should be a way to get brightness to work in hybrid mode. You said the value of

/sys/class/backlight/intel_backlight/brightness

is being changed, but nothing happens, right? You've probably tried xbacklight already (no luck?) and manually writing to the file like

sudo echo N > /sys/class/backlight/intel_backlight/brightness

where N is lower than the current value, could be worth a try. In case xbacklight works, make sure you've tried:

https://wiki.archlinux.org/index.php/Ba … ess_change

I'm not really familiar with dual graphics, so hopefully someone more knowledgable can offer better advice.

Tried xbacklight and manually writing to file. For the link, xbacklight doesn't work anyway.

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