FS#58392 - [linux-lts] No more screen brightness control with linux-lts 4.14 on Dell XPS 13

Attached to Project: Arch Linux
Opened by desbma (desbma) - Sunday, 29 April 2018, 13:47 GMT
Last edited by Andreas Radke (AndyRTR) - Wednesday, 02 May 2018, 19:50 GMT
Task Type Bug Report
Category Kernel
Status Closed
Assigned To Andreas Radke (AndyRTR)
Architecture All
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Screen brightness control is broken with linux-lts 4.14:
* the FN keys to control brightness do not work anymore (the other FN keys work as usual)
* the directory /sys/class/backlight is empty.
* xbacklight is unable to get or set current brightness

I can reproduce this with:
* linux-lts 4.14.35-1
* linux-lts 4.14.36-1

Everything works well when reverting back to linux-lts-4.9.78-1.

I'm on a Dell XPS 13 L322X (2nd gen., 2013) laptop.
This task depends upon

Closed by  Andreas Radke (AndyRTR)
Wednesday, 02 May 2018, 19:50 GMT
Reason for closing:  Fixed
Comment by Andreas Radke (AndyRTR) - Monday, 30 April 2018, 18:21 GMT
https://wiki.archlinux.org/index.php/Backlight#Kernel_command-line_options

Check "Tip" there and try various possible options. Backlight control may vary over several major kernel updates but usually keeps working in a different way.
Comment by loqs (loqs) - Monday, 30 April 2018, 22:37 GMT Comment by desbma (desbma) - Tuesday, 01 May 2018, 19:21 GMT
@AndyRTR Theses tips describe workarounds when several backlight control methods are in conflict. In my case I have none with kernel 4.14. The kernel simply does not detect any backlight driver. I only have the integrated Intel graphics, no discrete GPU.

@loqs No luck with 4.14.38, same issue.
Comment by loqs (loqs) - Tuesday, 01 May 2018, 19:24 GMT
Can you try the boot option video.only_lcd=0
Comment by desbma (desbma) - Tuesday, 01 May 2018, 20:48 GMT
With 'video.only_lcd=0' and linux-lts-4.14.37-1, everything is working as expected, like with 4.9.

Contrary to what I said previously, I did not test 4.14.38, only 4.14.37 (4.14.38 was not available yet in my mirror I guess).
Comment by desbma (desbma) - Wednesday, 02 May 2018, 16:07 GMT
I did test linux-lts-4.14.38-1 and the issue is fixed, even without 'video.only_lcd=0'.

Loading...