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I am using Toshiba Portege R835-P70 and function keys work as expected on Windows but they do not on Ubuntu 12.04. For e.g. Fn+F6 and Fn+F7 are supposed to change screen brightness but do not work.

What is the solution for this issue?

I tried adding GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash acpi_backlight=vendor“ to /etc/default/grub, but it introduces an additional problem in that the laptop wakes up to a faintly visible dark screen from hibernation.

I know this is an old issue, but if it is so common, why isn't there a simple solution to it and why isn't it incorporated in latest versions of Ubuntu?

Thanks.

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3 Answers

try this

open your terminal and type this sudo gedit /etc/default/grub and find a line GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash acpi_backlight=vendor“ and change it to like that . then close the editor and do sudo update-grub and give a restart . check it out now .

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I have already tried doing that. Above introduces an additional problem in that the screen boots to very faintly visible dark upon waking up from hibernation. –  abhinavkulkarni May 26 '12 at 7:03
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See a solution that worked on my Protege 705-P35 at Toshiba Portege Z830\Z835 [Linux Laptop Wiki]. To make the new script executable, type:

sudo chmod 755 /etc/pm/sleep.d/restore_brightness

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Welcome to Ask Ubuntu! Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. –  Oyibo Dec 10 '12 at 8:38
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try this!

This helped me, added to /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force acpi_backlight=vendor"

Then runupdate-grub and reboot.

Source: http://www.refreshit.info/2012/08/solved-brightness-increase-and-decrease.html

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