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I have just installed Fedora 18 KDE spin on my HP Pavillion dv6, but I have one problem: the brightness of the laptop is stuck at the highest; I have also two button that allow me to change the brightness, but when I click them a small window appears saying that the brightness is changing, but in reality nothing happens. How can I solve it?

If it helps, here is the /etc/default/grub file:

GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_CMDLINE_LINUX="rd.md=0 rd.lvm=0 rd.dm=0 $([ -x /usr/sbin/rhcrashkernel-param ] && /usr/sbin/rhcrashkernel-param || :) rd.luks=0 vconsole.keymap=it2 rhgb quiet$
GRUB_DISABLE_RECOVERY="true"
GRUB_THEME="/boot/grub2/themes/system/theme.txt"
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up vote 2 down vote accepted

Try adding "acpi_backight=vendor" to the end of the GRUB_CMDLINE_LINUX argument. The Linux kernel tries to control the backlight, but does a very poor job with some laptops. That kernel argument hands control of the backlight back to the vendor hardware.

The problem I have on my dv5 is that the backlight doesn't turn on at all without that argument. Not exactly the same problem you have, but it might be related.

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