Red Hat Bugzilla – Bug 773589
Screen brightness settings does not have any effect (2011 27inch iMac)
Last modified: 2012-06-01 14:14:07 EDT
+++ This bug was initially created as a clone of Bug #722745 +++
When you adjust the screen brightness, either in gnome or using the brightness
keys on the keyboard, the sliders change but there is no difference on the
actual brightness of the screen
HW: 2011 27 inch iMac, smolt:
I am using Refit to boot into Fedora.
--- Additional comment from email@example.com on 2011-08-05 13:41:12 EDT ---
Still happens in 2.6.40....
This was working fine after the initial install of fc16, but stopped working after upgrades.
Writing to /proc/acpi/ doesn't work so I suspect a kernel regression. Infact the relevant acpi files are missing completely now so perhaps the kernel config is missing something?
Scratch the last bit; I see it's moved to /sys. Still broken though - this has no effect:
echo 1 > /sys/class/backlight/acpi_video0/brightness
kernel-3.3.0-4.fc16 has been pushed to the Fedora 16 stable repository.
Please retest with this update.
Tried gnome settings and manual writing to /sys/class/backlight/acpi_video0/brightness. This value changes but brightness stays at max.
Anything I can do to help test, please shout. It's especially annoying since it worked fine with the initial install of fc16.
In fact it's worse than that. My imac now believes it has a battery and keeps hibernating after a few minutes due to critical battery. :(
I'll open a new bug for this.
Have you tested booting with the alt-key pressed in? If I do that I can change the brightness.
No I haven't tried that. Is this during rEFIt, grub.efi, kernel boot or what? Any ideas why it helps?
Fixed in Fedora 17. Yay!