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List:       opensuse
Subject:    Re: [opensuse] 13.1 - screen brightness stuck on high - unresponsive to fn keys - how to fix?
From:       "David C. Rankin" <drankinatty () suddenlinkmail ! com>
Date:       2014-07-14 21:09:07
Message-ID: 53C446F3.3080800 () suddenlinkmail ! com
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On 07/14/2014 03:23 PM, auxsvr@gmail.com wrote:
> On Monday 14 of July 2014 11:35:51 David C. Rankin wrote:
>> >    One new issue I have with 13.1 is my Toshiba laptop brightness is stuck
>> >on high (really high) and I cannot adjust it with the normal function keys.
>> >    Now it is just stuck. I can pop the 11.4 drive back in and it works fine.
>> >What could be causing this? Moreover, what could be the fix?
> Could you try setting the value in/sys/class/backlight/*/brightness to see
> whether the keys are registered to set the brightness level or not? For
> example, on my computer
>
> echo 100 > /sys/class/backlight/intel_backlight/brightness
>
> reduces backlight to low level and
>
> cat /sys/class/backlight/intel_backlight/brightness_max
>
> yields the maximum. If this works, probably some kernel module or special
> setting is required for the kernel to handle the special keys.

Hmm..,

   Now we are getting somewhere. This is interesting:

$ ll /sys/class/backlight/
total 0
lrwxrwxrwx 1 root root 0 Jul 14 15:34 acpi_video0 -> 
../../devices/pci0000:00/0000:00:01.0/0000:01:05.0/backlight/acpi_video0
lrwxrwxrwx 1 root root 0 Jul 14 15:34 radeon_bl0 -> 
../../devices/pci0000:00/0000:00:01.0/0000:01:05.0/drm/card0/card0-LVDS-1/radeon_bl0

   So I have 2 entries under /sys/class/backlight. The first acpi_video0:

$ l /sys/class/backlight/acpi_video0/
drwxr-xr-x 2 root root    0 Jul 14 10:56 power
-r--r--r-- 1 root root 4096 Jul 14 10:56 actual_brightness
-rw-r--r-- 1 root root 4096 Jul 14 10:56 bl_power
-rw-r--r-- 1 root root 4096 Jul 14 15:36 brightness
lrwxrwxrwx 1 root root    0 Jul 14 10:56 device -> ../../../0000:01:05.0
-r--r--r-- 1 root root 4096 Jul 14 10:56 max_brightness
lrwxrwxrwx 1 root root    0 Jul 14 15:36 subsystem -> 
../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Jul 14 15:36 type
-rw-r--r-- 1 root root 4096 Jul 14 15:36 uevent

$ cat /sys/class/backlight/acpi_video0/brightness
7


and the second radeon_bl0:

l /sys/class/backlight/radeon_bl0/
total 0
drwxr-xr-x 3 root root    0 Jul 14 05:44 .
drwxr-xr-x 4 root root    0 Jul 14 05:44 ..
drwxr-xr-x 2 root root    0 Jul 14 10:56 power
-r--r--r-- 1 root root 4096 Jul 14 10:56 actual_brightness
-rw-r--r-- 1 root root 4096 Jul 14 10:56 bl_power
-rw-r--r-- 1 root root 4096 Jul 14 10:56 brightness
lrwxrwxrwx 1 root root    0 Jul 14 10:56 device -> ../../card0-LVDS-1
-r--r--r-- 1 root root 4096 Jul 14 10:56 max_brightness
lrwxrwxrwx 1 root root    0 Jul 14 10:56 subsystem -> 
../../../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Jul 14 16:00 type
-rw-r--r-- 1 root root 4096 Jul 14 16:00 uevent

$ cat /sys/class/backlight/radeon_bl0/brightness
0

Judging from the values, /sys/class/backlight/acpi_video0/brightness is the 
correct one and a value of 7 is the brightest of the 8 steps [0-8]. Testing:

# for i in `seq 0 7`; do echo $i > /sys/class/backlight/acpi_video0/brightness; 
sleep 1; done

Steps perfectly through all 8 levels of brightness. How do we get the fn keys to 
work properly?



-- 
David C. Rankin, J.D.,P.E.
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