[ltp] brightness control erratic on T430s with 3.10 kernel
Andrew Turner
linux-thinkpad@linux-thinkpad.org
Mon, 02 Sep 2013 15:06:23 +0100
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On 02/09/13 14:19, Tamas Papp wrote:
> Hi,
>
> Since switching to the 3.10-2 from 3.9-1, I noticed that brightness keys
> don't change the LCD brightness of my T430s gradually, only in large
> steps, which is mapped rather erraticaly to what Linux thinks the
> brightness is.
>
> When I use the brightness keys,
>
> /sys/class/backlight/acpi_video0/brightness
> and
> /sys/class/backlight/acpi_video0/actual_brightness
>
> do change, but the LCD backlight remains unchanged. Then suddenly at
> around 50 it changes by a large step.
>
> --8<---------------cut here---------------start------------->8---
> tamas@tamas:~$ uname -a
> Linux tamas 3.10-2-amd64 #1 SMP Debian 3.10.7-1 (2013-08-17) x86_64
GNU/Linux
> tamas@tamas:~$ cat /sys/class/backlight/acpi_video0/max_brightness
> 100
> --8<---------------cut here---------------end--------------->8---
>
> and with the 3.9 kernel,
>
> --8<---------------cut here---------------start------------->8---
> tamas@tamas:~$ uname -a
> Linux tamas 3.9-1-amd64 #1 SMP Debian 3.9.8-1 x86_64 GNU/Linux
> --8<---------------cut here---------------end--------------->8---
>
> Does anyone have a fix, or some hints on how to debug this (eg maybe I
> could submit a bug report, but I need more specific info I guess).
>
> I found some bug reports that could be related, eg
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1098216
> but I am unsure if this is the same bug.
>
> Best,
>
> Tamas
This discussion may be of some help to you:
https://bbs.archlinux.org/viewtopic.php?id=158775
using acpi_osi='!Windows 2012' smoothed out the brightness control on my
t430s
Best wishes
Andrew
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On 02/09/13 14:19, Tamas Papp wrote:<br>
<span style="white-space: pre;">> Hi,<br>
><br>
> Since switching to the 3.10-2 from 3.9-1, I noticed that
brightness keys<br>
> don't change the LCD brightness of my T430s gradually, only
in large<br>
> steps, which is mapped rather erraticaly to what Linux thinks
the<br>
> brightness is.<br>
><br>
> When I use the brightness keys, <br>
><br>
> /sys/class/backlight/acpi_video0/brightness<br>
> and<br>
> /sys/class/backlight/acpi_video0/actual_brightness<br>
><br>
> do change, but the LCD backlight remains unchanged. Then
suddenly at<br>
> around 50 it changes by a large step.<br>
><br>
> --8<---------------cut
here---------------start------------->8---<br>
> tamas@tamas:~$ uname -a<br>
> Linux tamas 3.10-2-amd64 #1 SMP Debian 3.10.7-1 (2013-08-17)
x86_64 GNU/Linux<br>
> tamas@tamas:~$ cat
/sys/class/backlight/acpi_video0/max_brightness <br>
> 100<br>
> --8<---------------cut
here---------------end--------------->8---<br>
><br>
> and with the 3.9 kernel,<br>
><br>
> --8<---------------cut
here---------------start------------->8---<br>
> tamas@tamas:~$ uname -a<br>
> Linux tamas 3.9-1-amd64 #1 SMP Debian 3.9.8-1 x86_64
GNU/Linux<br>
> --8<---------------cut
here---------------end--------------->8---<br>
><br>
> Does anyone have a fix, or some hints on how to debug this
(eg maybe I<br>
> could submit a bug report, but I need more specific info I
guess).<br>
><br>
> I found some bug reports that could be related, eg<br>
> <a class="moz-txt-link-freetext" href="https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1098216">https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1098216</a><br>
> but I am unsure if this is the same bug.<br>
><br>
> Best,<br>
><br>
> Tamas</span><br>
This discussion may be of some help to you:<br>
<a class="moz-txt-link-freetext" href="https://bbs.archlinux.org/viewtopic.php?id=158775">https://bbs.archlinux.org/viewtopic.php?id=158775</a><br>
<br>
using acpi_osi='!Windows 2012' smoothed out the brightness control
on my t430s<br>
<br>
Best wishes<br>
Andrew<br>
<br>
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