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#1 2020-05-11 13:55:21

oliver_stotz
Member
Registered: 2020-05-02
Posts: 6

LCD brightness again (Lenovo T530)

Hi, dear Forum !

This topic has been brought up before, but i didn't find a solution for my special case, so here we go (again) ...

My FN-Keys to adjust the LCD brightness are not working.
The Keys themselves are recognized and the on-screen-display icons reflect the changes, but no brightness is adjusted.

This is on a Lenovo T530 Laptop, Debian 4.19.98-1, xfce4 v 4.12

I followed several threads here and on other forums, as this subject has been up for a long time and several workarounds were
proposed (Kernel Params, Scripts, /usr/share/polkit-1/actions/org.xfce.power.policy) - none of them worked for my case.

Lenovo T530 has a hybrid graphics card setup, so both INTEL and NVIDIA (or nouveau in my case) drivers are installed.

On inspecting /sys/class/backlight/, i discovered 2 symlinks, pointing to the graphic cards:

intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight                                                                      nv_backlight -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card1/card1-LVDS-2/nv_backlight

That is a bit strange as almost all other posts regarding this issue mention a "device" called "acpi_video0" which doesn't exist in my case. I guess this is why the "kernel params" method (GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor") doesn't work for me.

I installed a command line utility called "brightnessctl". With this i found out that the nv_backlight is the first and therefore "default" device that is adressed by the BRIGHTNESS keys (as i can use "brightnessctl" to query the status of each devices' brightness).

Is there any way i could make my FN-Brightness-Keys (Fn+F8 and Fn+F9 in my case) point to /sys/class/backlight/intel_backlight, rather than /sys/class/backlight/nv_backlight ?

Best - Oliver

________________________________________________________________________________

Just for completeness: This is my momentary workaround (f.e. to increase the brightness by 10%):

/usr/bin/brightnessctl -d intel* s +10%

I tried to bind this command to my FN Keys but it didn't work (they are probably "occupied" by the system) so i used another key combination, which works OK as a hack, but it's ugly (also i had to chmod u+s "brightnessctl" to make this work ...)

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#2 2020-05-11 17:11:34

ToZ
Moderator
From: Canada
Registered: 2011-06-02
Posts: 6,574

Re: LCD brightness again (Lenovo T530)

Are you using the proprietary nvidia driver? If so, does this help?

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#3 2020-05-14 06:41:01

oliver_stotz
Member
Registered: 2020-05-02
Posts: 6

Re: LCD brightness again (Lenovo T530)

Sorry, missed your reply ...

No, i didn't manage to make NVIDIA drivers work on my machine, so i'm using the INTEL and nouveau driver. this is my output when i do:

$ lspci -k | grep -EA3 'VGA|3D|Display'

00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
        Subsystem: Lenovo 3rd Gen Core processor Graphics Controller
        Kernel driver in use: i915
        Kernel modules: i915
--
01:00.0 VGA compatible controller: NVIDIA Corporation GF108M [NVS 5400M] (rev a1)
        Subsystem: Lenovo GF108M [NVS 5400M]
        Kernel driver in use: nouveau
        Kernel modules: nouveau

Best - Oliver

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#4 2020-05-14 09:33:52

alcornoqui
Member
Registered: 2014-07-28
Posts: 644

Re: LCD brightness again (Lenovo T530)

oliver_stotz wrote:

I guess this is why the "kernel params" method (GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor") doesn't work for me.

In the extensive Ubuntu guide to reporting backlight bugs, the last points refer specifically to Lenovo laptops:

15. For Lenovo computers, boot with only the kernel parameters:

thinkpad-acpi.brightness_enable=1 acpi_backlight=vendor

and comment on if brightness may be changed via hotkeys and/or brightness applet.

16. For Lenovo computers, execute at a terminal:

lsmod | grep thinkpad_acpi > "lsmod | grep thinkpad_acpi"

and attach uncompressed, untarred, and uncombined to your report.

Expanded in the Diagnostic Techniques section:

In some cases the ACPI BIOS provides the interfaces required to control the backlight through the generic ACPI interface, but the actual methods are not implemented. So the ACPI driver registers with the hardware and prevents any laptop specific drivers from doing so. In those cases it is possible to prevent the ACPI backlight driver from starting by adding the following line to the kernel boot parameters:

acpi_backlight=vendor

Unfortunately the thinkpad-acpi driver behaves differently, as it does not act on the ACPI driver being active or not, but on the ACPI methods being defined. Thus forcing the vendor specific driver to activate requires an additional:

thinkpad-acpi.brightness_enable=1

You can check to see if your system uses the thinkpad-acpi driver by using the following command:

lsmod | grep thinkpad_acpi

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#5 2020-05-15 21:20:33

oliver_stotz
Member
Registered: 2020-05-02
Posts: 6

Re: LCD brightness again (Lenovo T530)

Hi, thanks for your suggestions. But like many similar attempts before ... no dice.

Anyway here's my output from "lsmod | grep thinkpad_acpi", after the applied changes:

thinkpad_acpi         106496  1
nvram                  16384  1 thinkpad_acpi
battery                20480  1 thinkpad_acpi
video                  45056  3 thinkpad_acpi,i915,nouveau

Best - Oliver

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