help : brightness control

[dsuresh]

hi,,

i am using xubuntu 11.10 in samsung mini n148 laptop.. how to control brightness ...default key fn + down arrow not control the brightness ... please help...

thank u

[matt_symes]

Hi

Please post the output of

ls /sys/class/backlight

Kind regards

[dsuresh]

desktop@ubuntu:/etc/default$ ls /sys/class/backlight

acpi_video0 intel_backlight

Hi

Please post the output of

ls /sys/class/backlight

Kind regards

[matt_symes]

Hi

desktop@ubuntu:/etc/default$ ls /sys/class/backlight

acpi_video0 intel_backlight

Interesting. You have two entries. Let's see which one works (if either).

From the terminal type

sudo bash -c "echo 2 > /sys/class/backlight/acpi_video0/brightness"

Does that darken the screen ? If not try

sudo bash -c "echo 2 > /sys/class/backlight/intel_backlight/brightness"

Does that darken the screen ?

If the screen is darkened then type

sudo bash -c "echo 9 > /sys/class/backlight/ZZZZ/brightness"

and replace ZZZZ with which ever one darkened the screen.

Post back results.

EDIT: I have to pop out for a couple of hours. If no one else picks this up i will continue it later.

Kind regards

[dsuresh]

this command working :

sudo bash -c "echo 2 > /sys/class/backlight/intel_backlight/brightness"

...

[matt_symes]

Hi

this command working :

sudo bash -c "echo 2 > /sys/class/backlight/intel_backlight/brightness"

...

Can you post the output of

cat /proc/cmdline

It may help to resolve why you have two entries.

So we need to remove acpi_video0. Open a terminal and type

sudo modprobe -r video

Check your brightness buttons again.

Post back the results.

This will not persist after a reboot so, if it works, we can look at making it permanent.

Kind regards

[dsuresh]

desktop@ubuntu:~$ cat /proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-3.0.0-12-generic root=UUID=be5daad2-0aa9-49ca-b2e3-aae1cca3bee6 ro quiet splash vt.handoff=7


desktop@ubuntu:~$ sudo modprobe -r video
[sudo] password for desktop:
FATAL: Module video is in use.

[matt_symes]

Hi

desktop@ubuntu:~$ cat /proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-3.0.0-12-generic root=UUID=be5daad2-0aa9-49ca-b2e3-aae1cca3bee6 ro quiet splash vt.handoff=7

Nothing wrong with this command line.

desktop@ubuntu:~$ sudo modprobe -r video
[sudo] password for desktop:
FATAL: Module video is in use.

This is interesting and may be the reason why you have two entries.

Let's try to blacklist it and reboot.

From the terminal...

sudo bash -c "echo 'blacklist video' >> /etc/modprobe.d/blacklist.conf"

sudo reboot

Post back.

Kind regards

[dsuresh]

no.its not working....

[matt_symes]

Hi

The good thing is we know what the problem is. We just need to work out how to fix it.

Let's try to force it to use Intels version. Open a terminal and type

sudo nano /etc/default/grub

Look for the two line that say

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

and edit them so they say

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

Press ctrl + o to save and ctrl + x to exit.

Then type

sudo update-grub

Reboot your PC and try again.

Post back the results of

cat /proc/cmdline

and

ls /sys/class/backlight

after making the above changes.

Kind regards