1. Add "options thinkpad_acpi brightness_enable=1" to /etc/modprobe.d/acpi-video.conf
2. Update the initrd "sudo update-initramfs -u"
3. Add "acpi_backlight=vendor" to the kernel commandline (in /boot/grub/menu.lst)
But regardless of this, could you please attach the output of "sudo acpidump -o acpidump.txt" to this bug with a short comment to which Thinkpad it belongs. Thanks.
Have you tried the following?
1. Add "options thinkpad_acpi brightness_ enable= 1" to /etc/modprobe. d/acpi- video.conf =vendor" to the kernel commandline (in /boot/grub/ menu.lst)
2. Update the initrd "sudo update-initramfs -u"
3. Add "acpi_backlight
But regardless of this, could you please attach the output of "sudo acpidump -o acpidump.txt" to this bug with a short comment to which Thinkpad it belongs. Thanks.