Bug 1045341

Summary: Backlight level is reset to 0 when X starts or resumes from sleep
Product: [Fedora] Fedora Reporter: Unai Uribarri <unaiur>
Component: gdmAssignee: Ray Strode [halfline] <rstrode>
Status: CLOSED EOL QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 20CC: briancmonroe, collura, edwards, mplmpl, rstrode
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Last Closed: 2015-06-29 13:39:24 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Unai Uribarri 2013-12-20 08:20:49 UTC
Description of problem:

The X.org login manager turns off my screen.

When I turn on the computer, I can see correctly my screen. But when X.org loads, the screen seems to turn off. If I change back to text console, turns on again. Go back to X.org and it turns off.

If I enter through SSH and run as root:
"echo 100 > /sys/class/backlight/acpi_video0/brightness"

The screen turns on and I can see the login screen until the machine is suspended and the session locks. At resume, the backlight brightness is reset to 0 and I need to use SSH to reenable it.

Also, if I manage to blindly enter the user password correctly with the screen off, the backlight brightness is reconfigured automatically.


Version-Release number of selected component (if applicable):
Fedora 20

How reproducible:
Always

Steps to Reproduce:
1. Turn on the computer
2. Wait until X.org loads

Actual results:
The screen turns off

Expected results:
The screen remains on

Additional info:
My machine is a Toshiba Satellite P75-A7200

It has two backlight controls:
  /sys/class/backlight/acpi_vide0
  /sys/class/backlight/intel_backlight

Both operates correctly the backlight brightness, but the acpi one uses a 0-100 range and Intel uses a 0-4882 range. If I copy my brighness value from acpi_video0/brighness to intel_backlight/brighness, the screen turns off because the value is to low in the Intel range. May this be the problem?

Comment 1 Mike Lindner 2014-01-07 19:11:02 UTC
I have this problem too. Laptop is a Dell Latitude D630, (with second screen on external monitor). The external monitor does not dim/brighten, but when the laptop screen dims after not being used, it does not brighten on wakeup - I have to manually use the FN keys or run xbacklight or echo the appropriate value to the appropriate file.

Unlike the original poster, I am running F19, not 20. But liek the original poster I have 2 backlight controls that both seem to affect the laptop screen:

/sys/class/backlight/dell_backlight
/sys/class/backlight/intel_backlight

Comment 2 Mike Lindner 2014-01-07 19:12:06 UTC
FYI problem started when I upgraded to F 19 from F 17 - worked fine in 17 and before.

Comment 3 Unai Uribarri 2014-01-10 22:36:35 UTC
I've run this commands and the issue is partially solved:

yum install lightdm
systemctl disable gdm
systemctl enable lightdm

Now I can see the login screen, but as soon as I enter the password the backlight turns off again.

Comment 4 Unai Uribarri 2014-01-10 22:57:20 UTC
I suspect it's a common gnome component that runs both at gdm login screen and in the user session

Comment 5 Unai Uribarri 2014-01-14 19:33:59 UTC
I forgot to mention that if I turn on the computer with the AC power brick unplugged the LCD backlight turns on correctly. The issue only happens when the laptop is connected to AC power when booting.

Comment 6 Unai Uribarri 2014-01-14 20:00:54 UTC
It neither turns off if, at early boot, I change the permissions of /sys/class/backlight/intel_backlight/brightness to 0 (chmod 0 /sys/class/backlight/intel_backlight/brightness)

Comment 7 Unai Uribarri 2014-02-02 09:27:42 UTC
I booted the laptop the morning and the backlight worked correctly. I powered off and on three more times, but the backlight turned off always when running gdm.
This can be a race condition.

Comment 8 Brian Monroe 2014-04-09 22:01:17 UTC
I think I'm getting this same issue: I'm running an HP EliteBook 8460p. 

For me the screen is just dark and my lowest screen brightness is still visible, but responds to fn+brightness buttons. Also producible whenever I dock my computer and open/close/open the laptop screen. Screens used with the dock aren't affected.

Comment 9 Mark C. Edwards 2014-05-20 06:09:36 UTC
I also have  Dell D630 with the backlight issue. I read the 
/sys/class/backlight/intel_backlight/actual_brightness value as 255000 with a
very dim screen. Performing:
echo 255000 > /sys/class/backlight/intel_backlight/brightness bumped the screen
back to normal brightness. I booted and ran the laptop on the AC charger for all
instances of the test. Manipulating the function key brightness showed the expected screen icon, but did nothing.  Same failure to change the brightness
using the settings "power app". Both were restored to functionality after setting
the intel_backlight/brightness to 255000 with the echo command.  It sounds like a failure initialize the brightness "max" value in the driver.

Comment 10 Fedora End Of Life 2015-05-29 10:04:16 UTC
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Approximately 4 (four) weeks from now Fedora will stop maintaining
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Comment 11 Fedora End Of Life 2015-06-29 13:39:24 UTC
Fedora 20 changed to end-of-life (EOL) status on 2015-06-23. Fedora 20 is
no longer maintained, which means that it will not receive any further
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