Ubuntu
hotkeys package

Brightness indicator missing and automatic dim not working

Asked by RedSun

Hello dear community!

I had a problem with brightness so that my Acer Aspire One 756 (Celeron 847 / Intel HD Graphics) always was at 100%, which sucked my battery really fast. Thanks to Launchpad I could get a workaround, which made my brightness function buttons on the keyboard work as well as the slider in the system settings > brightness (see bottom of this question).

My current problem is that since I changed /etc/default/grub Ubuntu doesn't show anymore the notification box when pressing the function buttons for brightness in the top right corner of the display. The automatic dim which I've activated within system settings still doesn't affect anything, so still no automatic brightness dimming. After rebooting the system the brightness reverts back to 100%, but function buttons and slider in system settings are still working.

Is there any known solution for that?

Many thanks in advance.

______________________________________________________________________________

This is the workaround which helped me:

Run:
gksudo gedit /etc/default/grub

Find:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor acpi_osi=Linux"

Save the new file, close gedit and run:
sudo update-grub

Reboot to test

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Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#1

What is the question here please, thanks

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RedSun (red-sun-deactivatedaccount) said : 		#2

Ubuntus handling of backlight seems to be not that good.

Question is why the indicator bar in the top right corner of the display isn't showing up when I press "fn" + brightness up/down on my keyboard.

Second, why do I have to manually edit grub to be able to adjust the backlight at all? This should work out of the box.
Before applying the change to grub the indicator in the top right corner showed up, but nothing happened. Afterwards, the backlight is reacting, but the indicator doesn't show up.

Pretty weird and confusing. In my opinion this definitely has to be fixed.

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actionparsnip (andrew-woodhead666) said : 		#3

Because the kernel needs options to work with your particular hardware. Not all backlight implementations are identical so options are needed. Just like not all hardware works out of the box in Windows.

The indicator part I am unsure of. You could report a bug for that.

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RedSun (red-sun-deactivatedaccount) said : 		#4

Now I noticed that also backlight dimming (automatically) is working, but only after a short period of time (have to stop it for an exact value) it will get dimmed which is really annoying if you read something and it gets dimmed every 30 secs or so.

So far everything is working after applying the change to grub except for the visual indicator of display brightness when using the function buttons on my netbook. Since this is not a real problem (only a litte less comfortable) I can consider this as solved, but I maybe will raise a bug for this behaviour.

When you search the launchpad you will find a plenty of people with the same or similar issues, so I wouldn't count this as a single case or that hardware specific related to my netbook. There seems to be a general problem with handling backlight in Ubuntu / Linux kernel.