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Tasklist

FS#45801 - [linux] Backlight change delay when Fn Keys are used - intel_backlight

Attached to Project: Arch Linux
Opened by Facundo (klios) - Monday, 27 July 2015, 21:56 GMT
Last edited by Doug Newgard (Scimmia) - Tuesday, 03 October 2017, 02:42 GMT
Task Type Bug Report
Category Kernel
Status Closed
Assigned To Tobias Powalowski (tpowa)
Architecture x86_64
Severity Very Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 1
Private No

Details

Description:
Using Kernel 4.1, there is delay when changing mon backlight using fn keys. I tried with xbacklight -inc or -dec and there is no problem to change. Kernel versions < 4 are working fine. No delay at all

Additional info:
* package version(s)
* config and/or log files etc.


Steps to reproduce:
try to change more than two times mon backlight using fn keys(xf86monbrightnessdown/up) under any desktop enviroment (I've tried gnome, xmonad, qtile).
This task depends upon

Closed by  Doug Newgard (Scimmia)
Tuesday, 03 October 2017, 02:42 GMT
Reason for closing:  No response
Comment by Samantha McVey (samcv) - Thursday, 09 June 2016, 20:49 GMT
Please respond and let us know if you are still having this bug. If you are, please (!) give us some detailed information about your laptop (assuming laptop) model and other useful information. Thanks!
Comment by Facundo (klios) - Thursday, 09 June 2016, 20:56 GMT
My last attempt was on late 4.4 version, an the bug was still there. My laptop is a Lenovo Ideapad Flex 15 - The first version of that laptop. To add some info, the delay happen when you press XF86MonBrightnessDown/XF86MonBrightnessUp key multiple times or if you press and hold the key, the response for turning down or up the mon light will come far after the release of the key. If you press the key, and then release it, and wait a second a press it again there is no delay.

For example:
If I press and hold XF86AudioLowerVolume, the volume will go to 0% in many steps and stop.
If I press and hold XF86MonBrightessDown, the mon light will be the same, after a couple of seconds it will go to 0% in one step.
Comment by Samantha McVey (samcv) - Thursday, 09 June 2016, 21:03 GMT
Have you tried this on any other laptops running Linux and experienced what you consider the correct functionality (Either the same laptop and a different OS or a different laptop that is also running Linux)?
Correct me if I am wrong but the problem is pressing the button multiple times quickly in either repeatedly up brightness or repeat down brightness it starts lagging, same with holding the button down.
For me, using KDE and a Lenovo Thinkpad X220, I do get some sort of delay between changes in brightness on holding the key, but I am not noticing any lag if I hit the up or down brightness very quickly, and can increase or decrease as fast as I tap the button. Please let me know, thanks.
Comment by Facundo (klios) - Thursday, 09 June 2016, 21:16 GMT
I didn't try this on any other laptop. But on kernel version < 4 it work great. I think for that, it cannot be the laptop.
If I press multiple times quickly or hold the button, it will lag for a couple of seconds and then perform the action.
Comment by Samantha McVey (samcv) - Thursday, 09 June 2016, 21:30 GMT
This bug here may be related: https://github.com/linuxmint/cinnamon-settings-daemon/issues/17 and the developer there suggests it is a kernel module issue.
I also found this Ubuntu Forum post http://ubuntuforums.org/showthread.php?t=2208278&p=12942431 suggesting it could be caused by two backlight interfaces being exposed. Can you please run, and provide the output of:
$ for interface in /sys/class/backlight/*; do echo -e "\n $interface"; cat $interface/{brightness,max_brightness,actual_brightness}; done
AND
$ lsmod

Thanks.

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