Brightness controls issue on Debian 9

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Brightness controls issue on Debian 9

Postby zeroth » 2018-05-13 17:25

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 :
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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Re: Brightness controls issue on Debian 9

Postby Head_on_a_Stick » 2018-05-14 05:22

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: ... 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?
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