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I believe it's a big question among asus users, cause i've found tons of questions about "why do my backlight don't change with fn keys??".

Well... after to much researching and testing (I'm a linux noob btw :P), I found that the Fn keys change the value of the file /sys/class/backlight/asus_laptop/brightness. But, to change correctly the brightness, the file /sys/class/backlight/intel_backlight/brightness must be changed.

I even created a script to change it through bash, works alright and stuff... i just type ./brightness 50, where 50 means the % of the maximum brightness... but i still miss my Fn keys, for God's sake!!

Then I tried to simply change the symlinks that redirects the folders (asus_laptop and intel_backlight are symlinks to very opposed directions), but not even sudo was capable to change these symlinks...

In resume, I'm asking help to re-enable my Fn keys to work with the backlight brightness.

Thanks!

wjandrea
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gzmarques
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3 Answers3

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Ok, I think I found it. Edit your /etc/default/grub file:

sudo nano /etc/default/grub

Change the following line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to say this instead:

GRUB_CMDLINE_LINUX_DEFAULT="acpi_osi=! acpi_backlight=native idle=nomwait quiet splash"

Press CTRL + o and then press ENTER to save the file. Press CTRL + x to exit nano.

Finally, update grub and then reboot:

sudo update-grub

source

mchid
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  • That's it!! worked like a charm!! Thank you very much!! – gzmarques Apr 25 '16 at 19:25
  • @gzmarques Awesome! Don't forget to click the icon on the left to mark this as the accepted answer to your question. – mchid Apr 25 '16 at 19:31
  • @mchid Why idle=nomwait? – Pilot6 Jul 30 '16 at 17:56
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    @Pilot6 From http://redsymbol.net/linux-kernel-boot-parameters/ "Poll forces a polling idle loop that can slightly improve the performance of waking up a idle CPU, but will use a lot of power and make the system run hot. Not recommended. . . . idle=nomwait: Disable mwait for CPU C-states" – mchid Aug 02 '16 at 18:37
  • acpi_osi=! leads to failure on startup, I added another answer with a working solution for my asus rog flow x16 – rubo77 Mar 27 '24 at 10:42
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After I failed to activate the brightness button on my Asus laptop running vega8 graphic chip using methods above, I finally had it fix installing the proprietary AMD gpu linux driver 20.45. Apparently, the open source Mesa driver will not with the brightness button. And at this time of the writting, I have to downgrade my ubuntu kernel to 5.4 to work with AMD driver 20.45. Kernel 5.8 in ubuntu 20.04.2 seemed to have crippled many AMD and nVidia driver at this time.

coyote_sg
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This worked on my Asus rog flow x16 with AMD CPU:

Edit your /etc/default/grub file. Change the following line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to this instead:

GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=native"

(I also removed the "quiet splash", because I don't deen the graphical loading screen)

Finally, update grub and then reboot:

sudo update-grub
rubo77
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