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Old 01-20-2021, 07:15 PM   #1
mdkcore
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intel_backlight not working on -current


it happened after the last batch of update (glibc, kernel 5.10.9)

running intel_backlight gives me this error:
Code:
(intel_backlight:30159) intel-mmio-CRITICAL: Test assertion failure function intel_mmio_use_pci_bar, file intel_mmio.c:146:
(intel_backlight:30159) intel-mmio-CRITICAL: Failed assertion: !(error != 0)
(intel_backlight:30159) intel-mmio-CRITICAL: Last errno: 13, Permission denied
(intel_backlight:30159) intel-mmio-CRITICAL: Couldn't map MMIO region
Stack trace:
  #0 [<unknown>+0x40a630]
  #1 [<unknown>+0x407684]
  #2 [<unknown>+0x40708f]
  #3 [__libc_start_main+0xea]
  #4 [<unknown>+0x40715a]
Test (null) failed.
**** DEBUG ****
(intel_backlight:30159) intel-chipset-DEBUG: Test requirement passed: pci_dev
(intel_backlight:30159) intel-mmio-CRITICAL: Test assertion failure function intel_mmio_use_pci_bar, file intel_mmio.c:146:
(intel_backlight:30159) intel-mmio-CRITICAL: Failed assertion: !(error != 0)
(intel_backlight:30159) intel-mmio-CRITICAL: Last errno: 13, Permission denied
(intel_backlight:30159) intel-mmio-CRITICAL: Couldn't map MMIO region
(intel_backlight:30159) igt-core-INFO: Stack trace:
(intel_backlight:30159) igt-core-INFO:   #0 [<unknown>+0x40a630]
(intel_backlight:30159) igt-core-INFO:   #1 [<unknown>+0x407684]
(intel_backlight:30159) igt-core-INFO:   #2 [<unknown>+0x40708f]
(intel_backlight:30159) igt-core-INFO:   #3 [__libc_start_main+0xea]
(intel_backlight:30159) igt-core-INFO:   #4 [<unknown>+0x40715a]
****  END  ****
FAIL (-1.000s)
no additional information on dmesg or syslog
 
Old 01-21-2021, 12:16 AM   #2
RandomTroll
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I have the same kernel and libraries; mine works. Never used this program before; blanked my screen!
 
Old 01-21-2021, 07:31 AM   #3
mdkcore
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Quote:
Originally Posted by RandomTroll View Post
I have the same kernel and libraries; mine works. Never used this program before; blanked my screen!
are you running on a laptop? I'm on a thinkpad t490, intel_backlight is used here to control the screen brightness, but after the last bunch of updates it stopped working :/
 
Old 01-21-2021, 08:29 AM   #4
0XBF
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FWIW I get that same crash as OP when I run "intel_backlight" but my machine is still on Monday/Jan 18 changelog, without the glibc update. This is on a 2016 XPS-13 laptop.

Also my first time running that program. I usually just echo values into /sys/class/backlight/intel_backlight/brightness if I need to change the brightness and im not in a gui where the brightness keys work.
 
Old 01-21-2021, 08:40 AM   #5
0XBF
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One question: Perhaps it is just meant to be run as root? That works fine here. Running as a regular user gives the op's output from post 1
 
Old 01-21-2021, 10:32 AM   #6
mdkcore
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Quote:
Originally Posted by 0XBF View Post
One question: Perhaps it is just meant to be run as root? That works fine here. Running as a regular user gives the op's output from post 1
dunno, when I try to run with sudo just get this output:
Code:
[1]    20500 floating point exception  sudo intel_backlight
or sudo su -:
Code:
zsh: floating point exception  intel_backlight
 
Old 01-21-2021, 10:41 AM   #7
mdkcore
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just some more info; setting a value directly to /sys/class/backlight/intel_backlight/brightness works, but via xbacklight no (no errors):

Code:
sh $ sudo tee /sys/class/backlight/intel_backlight/brightness <<< 10000                                                                                                                                                                                      
10000
sh $ cat /sys/class/backlight/intel_backlight/{actual_brightness,brightness,max_brightness}                                                                                                                                                                  
10000
10000
24242
sh $ xbacklight -dec 10
sh $ cat /sys/class/backlight/intel_backlight/{actual_brightness,brightness,max_brightness}                                                                                                                                                                  
10000
10000
24242
also, it's quite strange the values from /sys/class/backlight/intel_backlight/, but can't confirm if they are right at the moment
EDIT: tested on another machine and values are correct

Last edited by mdkcore; 01-21-2021 at 11:10 AM.
 
Old 01-21-2021, 03:08 PM   #8
Candelabrus
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Same kernel and last update too.

without root, same error from op and with root show me this message.

Code:
current backlight value: 100%
 
Old 01-21-2021, 04:12 PM   #9
mumahendras3
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Any possibility that this is caused by the use of Xorg modesetting driver instead of the intel one? As stated in the ChangeLog, newer intel graphics will use the modesetting driver by default and AFAIK xbacklight doesn't work with the modesetting driver. But, I don't know about intel_backlight though (I never use it).
 
Old 01-21-2021, 05:46 PM   #10
0XBF
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I went and tried this "intel_backlight" on three different machines with intel cards and it doesn't work on any of them.

1. Slackware 14.2 on an Eee 1000H - Running "intel_backlight" as a user still errors. The message is different but reports an error with "intel_mmio_use_pci_bar", so similar I guess. Running as root/sudo reports a percentage but setting a value does nothing.

2. Slackware64 current on an XPS-13 - Running as user is same error as post 1, running as root reports percentage, but setting a value doesn't work.

3. Slackware64 current on a 2011 MBP, last updated in June 2020 (kernel 5.4.46) and sitting on a shelf since then - Exact same behavior as the XPS-13, although this one reports the percentage as 2180% or something ridiculous like that.

I'm beginning to doubt this program ever worked, or I'm just getting lucky on my machines.
 
Old 01-21-2021, 08:16 PM   #11
RandomTroll
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Quote:
Originally Posted by mdkcore View Post
are you running on a laptop?
Yes, a Toshiba Satellite.

Quote:
Originally Posted by 0XBF View Post
One question: Perhaps it is just meant to be run as root? That works fine here. Running as a regular user gives the op's output from post 1
Same here. I hoped it wouldn't work as non-root, so only tried it as root; trying it as non-root returns that error. It should just tell you it can't run.

Quote:
Originally Posted by mumahendras3 View Post
Any possibility that this is caused by the use of Xorg modesetting driver instead of the intel one?
X makes no difference.
 
Old 01-24-2021, 12:58 AM   #12
djemos
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create a 20-intel.conf file with following lines

Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "Backlight" "intel_backlight"
EndSection

copy it to /etc/X11/xorg.conf.d/20-intel.conf

Then restart X
type xbacklight -20

Last edited by djemos; 01-24-2021 at 02:46 AM.
 
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Old 01-24-2021, 07:58 AM   #13
Andersen
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I have similar issue with xbacklight. I cannot set up screen brightness and when I try, I get: "No outputs have backlight property". Intel CPU with HD 620 graphics as primary and NVIDIA as secondary.

EDIT:

I can confirm that this solved the problem I had:

Quote:
Originally Posted by djemos View Post
create a 20-intel.conf file with following lines

Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "Backlight" "intel_backlight"
EndSection

copy it to /etc/X11/xorg.conf.d/20-intel.conf

Then restart X
type xbacklight -20
Thanks djemos!

Last edited by Andersen; 01-24-2021 at 08:09 AM. Reason: solved
 
Old 01-24-2021, 08:36 AM   #14
BrunoLafleur
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Quote:
Originally Posted by Andersen View Post
I have similar issue with xbacklight. I cannot set up screen brightness and when I try, I get: "No outputs have backlight property". Intel CPU with HD 620 graphics as primary and NVIDIA as secondary.

EDIT:

I can confirm that this solved the problem I had:



Thanks djemos!
That is because the latest Slackware current uses the modesetting Xorg driver for Intel chipset.
Putting the xorg conf like said make Xorg reuse the intel Xorg driver. The only useful line is Driver "intel"

The modesetting driver is unable to deal with backlights and don't work with xbacklight. You should use other tools for backlights and maybe put acpi_backlight=video in the kernel append line at boot for having power control with backlights.
 
2 members found this post helpful.
Old 01-24-2021, 12:28 PM   #15
djemos
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Quote:
Originally Posted by BrunoLafleur View Post
That is because the latest Slackware current uses the modesetting Xorg driver for Intel chipset.
Putting the xorg conf like said make Xorg reuse the intel Xorg driver. The only useful line is Driver "intel"

The modesetting driver is unable to deal with backlights and don't work with xbacklight. You should use other tools for backlights and maybe put acpi_backlight=video in the kernel append line at boot for having power control with backlights.
Putting acpi_backlight=video in the kernel append line at boot without use other tool is working also but i have to press the key for reduce screen light for some seconds. While the other method with the file, is working immediately for reducing or increasing screen light.
 
  


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