This laptop is configured with an integrated and a dedicated graphics card (Nvidia Quadro).
I use just the dedicated graphics card and I've disabled Optimus OS detection from BIOS.
I get this odd message on my kernel logs:
Code: Select all
sudo dmesg | grep thinkpad
[ 3.898378] thinkpad_acpi: ThinkPad ACPI Extras v0.25
[ 3.898380] thinkpad_acpi: http://ibm-acpi.sf.net/
[ 3.898381] thinkpad_acpi: ThinkPad BIOS 83ET78WW (1.48 ), EC unknown
[ 3.898382] thinkpad_acpi: Lenovo ThinkPad T420, model 4178A2G
[ 3.899763] thinkpad_acpi: radio switch found; radios are enabled
[ 3.899788] thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, supported by the ACPI video driver
[ 3.899789] thinkpad_acpi: Disabling thinkpad-acpi brightness events by default...
[ 3.902921] thinkpad_acpi: Standard ACPI backlight interface available, not loading native one
[ 3.906025] input: ThinkPad Extra Buttons as /devices/platform/thinkpad_acpi/input/input9
The /sys/class/backlight/ subsystem is not working and I can not change my screen brightness through Gnome slider or the Fn keys (home+end).
However xbacklight works fine.
Part of xorg.conf:
Code: Select all
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "NVS 4200M"
Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection
Code: Select all
$ acpi_listen
video/brightnessdown BRTDN 00000087 00000000
video/brightnessup BRTUP 00000086 00000000
I 've tried booting with many different parameters and tried every other solution I read online but none of that fixed it.
How can I fix this issue to work seamlessly just like it worked with the intel graphics card? I read somewhere that Optimus configurations may demonstrate this behavior but is there a solution?