Ubuntu 14.04 brightness problem (Lenovo Z500)

Solution 1:

Two years ago I bought this laptop which works pretty well with Linux. When I upgraded to my new distro, Elementary OS Freya, I noticed the problem that backlight was unable to change. I could change it only on grub screen. After trying every guide on the internet I partially solved the issue by downgrading the kernel (and the related Intel graphics driver) to version 3.13. Yesterday I gave another try. It was very lucky :)

Here the solution:

On the grub configuration file /etc/default/grub modify the following line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

by adding this string: acpi_backlight=vendor.

In my case it is:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Update grub by launching:

sudo update-grub

Then create a xorg configuration file like this:

/usr/share/X11/xorg.conf.d/80-backlight.conf

and copy in it this text:

Section "Device"
    Identifier  "Intel Graphics"
    Driver      "intel"
    Option      "AccelMethod"     "sna"
    Option      "Backlight"       "ideapad"
    BusID       "PCI:0:2:0"
EndSection

Save the file, Reboot, Enjoy :-)

This trick could work on other Lenovo Ideapad laptops. I tested on Lenovo Ideapad z500 on Elementary OS Freya and Debian 8 Jessie.

If you have complitely another laptop you can try this way: Modify grub like in the first part of the guide, update grub, reboot, then verify what backlight "drivers" (I don't know what they are) are being listed. Give:

ls /sys/class/backlight/

and if it gives:

backlight_driver1
backlight_driver2
backlight_driver3

Then create the xorg file with one of the drivers in the list:

Section "Device"
    Identifier  "Intel Graphics"
    Driver      "intel"
    Option      "AccelMethod"     "sna"
    Option      "Backlight"       "backlight_driver1"
    BusID       "PCI:0:2:0"
EndSection

And reboot. If it works, enjoy, otherwise modify the file with another one in the list the same way.

Solution 2:

You could try this

1. Add GRUB_CMDLINE_LINUX="acpi_backlight=vendor" to /etc/default/grub.
2. Update grub and reboot. Execute sudo update-grub && reboot.