Friday, November 18, 2011

Fedora 16 : LCD screen backlight brightness on Acer Aspire 5742 issue

Tonight I found a temporary solution on my Acer Aspire 5742 (thanks to GusCarracedo for
the clue) how to change a backlight brightness of my screen.
# ls -R /sys/class/backlight/
acpi_video0 intel_backlight

# cat /sys/class/backlight/intel_backlight/brightness
<- This was an original value I found

# cat /sys/class/backlight/intel_backlight/max_brightness

# echo "400" > /sys/class/backlight/intel_backlight/brightness perfectly fine, as a temporary solution of course.

Changing acpi_video0/brightness had no effect.

Please check this out as well:
It is for i915 chip (found also in Aspire 5742).
I have intel_backlight interface, but it looks gnome-power-manager is not updated, so I am investigating this now.

I hope this will help Fedora developers to fix this issue permanently once and
for all.

Dmitriy Kalmykov suggested how to fix the issue (bug 753012and it seems to work also on my Acer Aspire 5742, so I would say it is worth to try and big thanks to Dmitriy :)

Open '/boot/grub2/grub.cfg' for editing.
Ignore the line '# DO NOT EDIT THIS FILE'.
Find the proper bootline which boots your kernel and add
'acpi_backlight=vendor' parameter in kernel options.

The part of my '/boot/grub2/grub.cfg' edited looks like that:

menuentry 'Fedora (3.1.1-2.fc16.x86_64)' --class fedora --class gnu-linux
--class gnu --class os {
 set gfxpayload=keep
 insmod gzio
 insmod part_msdos
 insmod ext2
 set root='(hd0,msdos1)'
 search --no-floppy --fs-uuid --set=root 8cb738a0-95f4-4fe7-9c42-7d95aa3cc8da
 echo 'Loading Fedora (3.1.1-2.fc16.x86_64)'
 linux /vmlinuz-3.1.1-2.fc16.x86_64
root=UUID=76b94cf5-3dad-4b63-899e-2c99849fdde3 ro LANG=ru_RU.UTF-8
rd.lvm=0 quiet rhgb rd.luks=0  KEYTABLE=us acpi_backlight=vendor
 echo 'Loading initial ramdisk ...'
 initrd /initramfs-3.1.1-2.fc16.x86_64.img