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F19 Macbook Air Brightness Issue after suspend

asked 2013-07-21 21:22:55 -0500

matthicksj gravatar image

updated 2013-07-29 09:07:50 -0500

FranciscoD_ gravatar image

On a clean reboot, my brightness hotkeys and setting manually (e.g. su -c "echo 10 > /sys/class/backlight/intel_backlight/brightness") works fine. The brightness 'steps' increment smoothly from 0% to 100% brightness. However, after a suspend / restore, there are only two effective brightness steps - 0% or about 95%. Anything below 95% brightness and the screen turns off, and anything above that and it's about 95% brightness. The hotkeys still technically work and show the percentage correctly (and /sys/class/backlight/intel_backlight/brightness appears to show the correct value too), but the actual screen is either all on or all off.

mhicks@localhost ~$ cat /sys/class/backlight/intel_backlight/brightness 
mhicks@localhost ~$ cat /sys/class/backlight/intel_backlight/max_brightness 

I've tried setting acpi_backlight=vendor in my kernel command line which didn't work and I've tried the various rc.local scripts to set the brightness on boot and another script in /etc/pm/sleep.d/ to set the brightness on sleep but that didn't work as well.

Any ideas?

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I've opened the following bug to hopefully move things along. Please comment if you experience the same issue:

matthicksj gravatar imagematthicksj ( 2013-07-29 09:22:38 -0500 )edit

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answered 2013-07-28 10:34:12 -0500

On F19, try adding a script to /lib/systemd/system-sleep for Post to force the brightness

echo '15' | sudo tee /sys/devices/pci0000\:00/0000\:00\:02.0/backlight/acpi_video0/brightness

Also note this bug report in ubuntu:

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Accessing through /sys/devices/pci* (or any other location) doesn't work for me. I can't find a backlight control in that structure. I did try using my commands above in the systemd script location but while it sets the backlight, it still doesn't have an effect.

matthicksj gravatar imagematthicksj ( 2013-07-29 09:21:38 -0500 )edit

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Asked: 2013-07-21 21:22:55 -0500

Seen: 1,199 times

Last updated: Jul 29 '13