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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Screen sometimes jumps to full brightness on resume from suspend"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108703">108703</a>
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<th>Summary</th>
<td>Screen sometimes jumps to full brightness on resume from suspend
</td>
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<th>Product</th>
<td>xorg
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
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<th>Component</th>
<td>Driver/intel
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<th>Assignee</th>
<td>chris@chris-wilson.co.uk
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<th>Reporter</th>
<td>luke.schlather@gmail.com
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<pre>At night, I usually turn my brightness down as far as it will go using the
brightness keys. This makes it dim, but visible and not off. When I walk away
for a while, the screen goes to sleep, and when I come back and move the mouse,
the screen jumps to full brightness, which is very unpleasant at night.
Investigating, it seems that the brightness in intel_backlight is getting reset
to 4437, but the one in acpi_video0 reads 0.
This can be triggered by running xset dpms force standby. Here's the
conflicting brightness values:
$ for file in brightness max_brightness actual_brightness;
> do
> for directory in /sys/class/backlight/intel_backlight/
/sys/class/backlight/acpi_video0/
> do
> echo $directory$file : $(cat $directory$file)
> done
> done
/sys/class/backlight/intel_backlight/brightness : 4437
/sys/class/backlight/acpi_video0/brightness : 0
/sys/class/backlight/intel_backlight/max_brightness : 4437
/sys/class/backlight/acpi_video0/max_brightness : 15
/sys/class/backlight/intel_backlight/actual_brightness : 4437
/sys/class/backlight/acpi_video0/actual_brightness : 0
After I press the button to increase the brightness one notch, they are back in
sync, and then I can turn it back down as well.
$ for file in brightness max_brightness actual_brightness;
> do
> for directory in /sys/class/backlight/intel_backlight/
/sys/class/backlight/acpi_video0/
> do
> echo $directory$file : $(cat $directory$file)
> done
> done
/sys/class/backlight/intel_backlight/brightness : 53
/sys/class/backlight/acpi_video0/brightness : 1
/sys/class/backlight/intel_backlight/max_brightness : 4437
/sys/class/backlight/acpi_video0/max_brightness : 15
/sys/class/backlight/intel_backlight/actual_brightness : 53
/sys/class/backlight/acpi_video0/actual_brightness : 1
This is on a fresh install of Xubuntu 18.04 with default packages including the
latest version of the i915 Intel Driver which is active. Seems like a
regression from Xubuntu 16.04, which I ran on the same laptop without this
issue.
I initially filed this as a bug in XFCE power manager but after some
troubleshooting there I can reproduce the same issue under Gnome as well.
Original bug with troubleshooting:
<a href="https://bugs.launchpad.net/ubuntu/+source/xfce4-power-manager/+bug/1782177">https://bugs.launchpad.net/ubuntu/+source/xfce4-power-manager/+bug/1782177</a></pre>
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