Bug 748182

Summary: regression from f15: brightness control on Samsung n210 (Atom N450)
Product: [Fedora] Fedora Reporter: Yann Droneaud <yann>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED INSUFFICIENT_DATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 16CC: dennis, gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
Target Milestone: ---   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2011-11-29 02:24:53 UTC Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Flags
Little video to demonstrate the brightness setting problem none

Description Yann Droneaud 2011-10-22 20:09:12 UTC 
After booting Fedora-16-TC-x86_64-Live-Desktop, I have tried the brightness control using keyboard shortcut.

I can set brightness down only to the "lower" level of brightness.
When setting brightness up, I can set it to "a little higher than lower", then "high" lever.

On Fedora F15 with updated kernel, I was able to choose brighness level, step by step.
Comment 1 Yann Droneaud 2011-10-22 20:10:57 UTC 
Created attachment 529637 [details]
Little video to demonstrate the brightness setting problem
Comment 2 Yann Droneaud 2011-10-24 17:34:31 UTC 
After looking at bug #745977 I have found the different brightness values reported by kernel

At high level (default)

    8 /sys/devices/platform/samsung/backlight/samsung/actual_brightness 
12421 /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness
    7 /sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/actual_brightness


When lowering the brightness

    0 /sys/devices/platform/samsung/backlight/samsung/actual_brightness 
12421 /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness
    7 /sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/actual_brightness

When increasing the brightness

    1 /sys/devices/platform/samsung/backlight/samsung/actual_brightness 
12421 /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness
    7 /sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/actual_brightness

After increasing the brightness

    8 /sys/devices/platform/samsung/backlight/samsung/actual_brightness 
12421 /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness
    7 /sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/actual_brightness


I have later found some information in bug 737108 comment 2
https://bugzilla.redhat.com/show_bug.cgi?id=737108#c2

https://lkml.org/lkml/2011/4/20/1
https://lkml.org/lkml/2011/5/11/548

So this seems to be a kernel bug
Comment 3 Josh Boyer 2011-11-02 16:15:37 UTC 
There are a number of fixes in the latest rawhide kernel in this area.  Would you be willing to install that and let us know if the issue is resolved?