Not able to control Brightness in my VAIO CW15FG laptop

**wizardvenkat** · November 14th, 2012

I've installed Ubuntu 12.10 recently.
When ever I press Fn keys along with F5/F6 it shows that the brightness decreases / increases accordingly. But no difference on the screen.

I tried modifying the grub , xorg.conf files as mentioned in many other posts. But none helped me. I'm new to the Ubuntu environment and I'm completely clueless about what to do.

In my /sys/class/backlight directory, I find two folders (shortcuts)
nv_backlight &
sony
And when I change my brightness I find the value changes accordingly in brightness file present inside 'sony' folder.

Earlier I tried to install nvidia driver for my G210M graphics card and failed. I get a blank screen after the boot screen after installation. So reverted the settings to work on my default driver

I even tried kubuntu 12.10 live cd (KDE environment) and found the same problem there.
Plz someone help me with this brightness issue. it is even Ok for me to work without my nvidia drivers as I'm not a big fan of games.

**Toz** · November 14th, 2012

Originally Posted by wizardvenkat

I tried modifying the grub

What modifications did you make to grub? Did you try the acpi_backlight=vendor parameter?

**wizardvenkat** · November 14th, 2012

Originally Posted by Toz

What modifications did you make to grub? Did you try the acpi_backlight=vendor parameter?

This info is available in my /etc/default/grub
GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=sony"
GRUB_CMDLINE_LINUX="acpi_backlight=sony"

**Toz** · November 14th, 2012

The parameter should say exactly acpi_backlight=vendor, the vendor keyword indicating to use the vendor-specific driver instead of the acpi driver.

acpi_backlight=sony is not a valid parameter.

Make sure to also run:

Code:

sudo update-grub

...afterwards to commit the edits.

If it still doesn't work on reboot, can you post back the results of:

Code:

cat /proc/cmdline

...and the contents of your dmesg log file? Use this command:

Code:

pastebinit /var/log/dmesg

...and post back the link that is generated.

**wizardvenkat** · November 15th, 2012

acpi_backlight=vendor statement is also not working.

These are my results for cat proc/cmdline :

BOOT_IMAGE=/boot/vmlinuz-3.5.0-18-generic root=UUID=446e1f28-d397-4eef-a7fb-fa0eda88129a ro acpi_backlight=vendor quiet splash acpi_backlight=vendor vt.handoff=7

And my PasteBin URL is here

**Toz** · November 15th, 2012

Can you remove both of the acpi_backlight=vendor parameters from grub and reboot the computer? This time post back the results of:

Code:

cat /proc/cmdline
lsmod

...and the links to the following two log files:

Code:

pastebinit /var/log/dmesg
pastebinit /var/log/Xorg.0.log

You also mentioned that you tried to install the nvidia driver and that it didn't work. How did you try to install it? Was it through the additional drivers tab via:

Code: