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Brightness controls issue on Debian 9

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zeroth
Posts: 1
Joined: 2018-05-13 16:46

Brightness controls issue on Debian 9

#1 Post by zeroth »

Hi everyone

I am not very experienced with Linux so I hope the question won't seem too stupid.
I have just managed to install Debian 9 (Gnome) on an Imac (from mid 2011). Although most things seem to be ok I am having troubles with brightness.
The brightness bar in the interface is all fine, however if I move the cursor down, the screen doesn't respond.

This is all I have :
/sys/class/backlight
acpi_video0 radeon_bl0

For acpi_video0:
max_brightness is set at 15.
when I change the brightness level with the cursor my acpi_video0 outputs for brightness and actual_brightness change accordingly.

For radeon_bl0:
max_brightness is set at 255
actual_brightness and brightness are set at 103 and won't ever change when I interact with the interface controller for brightness.

I can adjust the screen brightness this way :
echo 100(or whatever number) | sudo tee /sys/class/backlight/radeon_bl0/brightness

I would like to know how I could possibly fix the link with the interface controls ?

Thank you

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Head_on_a_Stick
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Re: Brightness controls issue on Debian 9

#2 Post by Head_on_a_Stick »

zeroth wrote:echo 100(or whatever number) | sudo tee /sys/class/backlight/radeon_bl0/brightness
You can drop the echo command and use a here string instead of the pipe:

Code: Select all

sudo tee /sys/class/backlight/radeon_bl0/brightness <<<"100"
But for actually fixing the problem try one of the kernel command line parameters listed here:

https://wiki.archlinux.org/index.php/Ba ... ne_options

Perhaps the keys will start working if there is only one folder under /sys/class/backlight

Also, have you installed the non-free firmware required by your video card?
deadbang

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