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How to fix backlight issue on IdeaPad y510p

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Today I decide to switch to latest kernel (3.17-rc1) on my IdeaPad y510p. I hit only one annoying problem until now – after booting my main screen was dimmed. I tried all instructions from top google hits for all possible configurations of keywords linux, y510p, backlight issue, etc.

Especially I tried all methods from Arch Wiki.

Finally I found solution, by greping modinfo for my Intel graphics card:

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[23:55:24] pietrushnic:~ $ sudo modinfo i915|grep backlight
parm:           invert_brightness:Invert backlight brightness (-1 force normal, \
 0 machine defaults, 1 force inversion), please report PCI device ID, subsystem \
vendor and subsystem device ID to dri-devel@lists.freedesktop.org, if your \
machine needs it. It will then be included in an upcoming module version. (int)

So simple modification in /etc/default/grub by adding kernel parameter to GRUB_CMDLINE_LINUX_DEFAULT fix the issue:

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# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="rcutree.rcu_idle_gp_delay=1 i915.invert_brightness=1"
GRUB_CMDLINE_LINUX=""
(...)

After that:

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sudo update-grub

And all things should work fine.

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