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Hello,
My on my laptop, an HP omen 15-ceo47nf, I'm not able to adjust the backlight.
The computer have hybrid graphics provided by an Intel Core i5-7300HQ and an nvidia GTX 1060 mobile 6GB.
when I start x then kill it the tty is brighter but it does not affect x servers.
I already tried to use xbacklight, light, and changing the value of '/sys/class/backlight/nvidia_0/brightness' and even if the value change it has no effect on the backlight.
I also try to add this option in the device section of '/etc/xorg.conf' but it has no effect:
Option "RegistryDwords" "EnableBrightnessControl=1"
I have this warning in the Xorg log but I have no clue of wat to do whith it:
[ 827.271] (WW) VGA arbiter: cannot open kernel arbiter, no multi-card support
I don't know what did I have to look for to fix the issue so any help is welcome.
thank you in advance for your help.
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Try adding
acpi_backlight=vendor
to your kernel boot command line
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It has no effect.
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What is the output of ls -l /sys/class/backlight/*/
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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total 0
-r--r--r-- 1 root root 4096 Jul 6 16:20 actual_brightness
-rw-r--r-- 1 root root 4096 Jul 6 16:20 bl_power
-rw-rw-r-- 1 root video 4096 Jul 6 06:48 brightness
lrwxrwxrwx 1 root root 0 Jul 6 16:20 device -> ../../../0000:01:00.0
-r--r--r-- 1 root root 4096 Jul 6 16:20 max_brightness
drwxr-xr-x 2 root root 0 Jul 6 16:20 power
-r--r--r-- 1 root root 4096 Jul 6 16:20 scale
lrwxrwxrwx 1 root root 0 Jul 6 16:20 subsystem -> ../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Jul 6 16:20 type
-rw-r--r-- 1 root root 4096 Jul 6 16:20 uevent
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Looks good. Now the output of
ls /sys/class/backlight
cat /sys/class/backlight/*/max_brightness
and
cat /sys/class/backlight/*/*brightness
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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ls /sys/class/backlight
nvidia_0
cat /sys/class/backlight/*/max_brightness
100
cat /sys/class/backlight/*/*brightness
100
100
100
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Opps, I had an extra * in there. But, no matter, it works
Assuming your user is in the wheel group, lets try sudo bash -c "echo 50 > /cat/sys/class/backlight/*/brightness"
I hope that changes the brightness. If not, post any errors from that command and cat /sys/class/backlight/*/*brightness again
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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How to Ask Questions the Smart Way
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I tried:
sudo bash -c "echo 50 > /cat/sys/class/backlight/*/brightness"
but ther is no /cat folder
I think you wanna me to use
sudo bash -c "echo 50 > /sys/class/backlight/*/brightness"
and it dosen't change the brightness.
cat /sys/class/backlight/*/*brightness:
50
50
100
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Clearly I need more coffee this morning
sudo bash -c "echo 50 > cat /sys/class/backlight/*/brightness"
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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Well, that shows the command was accepted. Is this with or without the suggestion of rep_movsd for the command line option ?
Last edited by ewaller (2021-07-06 15:06:29)
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way
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it was without the command line option. I reboot with and retry
sudo bash -c "echo 50 > cat /sys/class/backlight/*/brightness"
but it has no effects on the brightness and doesn't change the values I get when I do
cat /sys/class/backlight/*/*brightness
100
100
100
. I retried
sudo bash -c "echo 50 > /sys/class/backlight/*/brightness"
and it doesn't change the brightness but it change the values:
cat /sys/class/backlight/*/*brightness
50
50
100
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It would appear that the backlight has some other means of controlling it on this laptop. I am puzzled why there is no structure for intel_backlight under /sys/class/backlight
Can we try this again after rebooting with the kernel command line option acpi_backlight=native
?
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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It is the same as with acpi_backlight=vendor.
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As a sanity check, what is the output of cat /proc/cmdline
?
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way
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cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-linux root=UUID=81c5d39f-d8ef-4677-be87-9efc8c82dba4 rw loglevel=3 quiet acpi_backlight=native
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