Arch Linux

lviggiani

Member

Registered: 2014-02-28

Posts: 141

Laptop display brigthness always pushed to 100% when GDM starts

Hi all,
since the latest updates, whenever the system boots up and gdm starts, the display brightness stays at 100% instead of restoring previous session value as it was happening until few days ago.
"Suspect" updates to me are:

linux-3.15.7-1
xorg-server-1.16.0-6
xf86-video-intel-2.99.914-2

This is happening on Dell XPS laptop with Intel HD Graphics 3000 and Arch Linux 64 bit.
Is anyone having the same issue? Is there any workaround to try out?
Thanks!

Last edited by lviggiani (2014-07-31 18:56:56)

Pse

Member

Registered: 2008-03-15

Posts: 413

Re: Laptop display brigthness always pushed to 100% when GDM starts

This always happens to me as well (Intel HD4000 user here). In fact, there's a systemd unit that's supposed to take care of the brightness during boot, but it does nothing in my case (see systemd-backlight). It's a very minor issue so I haven't really investigated. I do know changing the brightness by writing to /sys/class/backlight/intel_backlight/brightness works (and the brightness keys work too), so I don't really know what's keeping things from working during boot.

Last edited by Pse (2014-08-01 02:45:30)

lviggiani

Member

Registered: 2014-02-28

Posts: 141

Re: Laptop display brigthness always pushed to 100% when GDM starts

Hi Pse,
thank you very much for your reply. I wasn't aware of systemd-backlight. I'll investigate why it's failing.
You're right, it's a minor issue but it's also annoying to me as I normally keep display very dim.
I used to read/write to /sys/class/backlight/intel_backlight/brightness in the past but I'd rather fix it in the "official" way now that I know about that systemd-backlight service.
I'll keep you posted on any progress from my side.

lviggiani

Member

Registered: 2014-02-28

Posts: 141

Re: Laptop display brigthness always pushed to 100% when GDM starts

Ok I tought I solved by

systemctl stop systemd-backlight@backlight:acpi_video0.service
rm /var/lib/systemd/backlight/*

then adjust brigthness with fn keys, then

systemctl start systemd-backlight@backlight:acpi_video0.service

Setting was kept at first reboot, but from second reboot onward it started again to set brightness to 100%.
It seems that the issue is at stop. It look that service is stopped after gdm, when screen brightness goes to 100%.

Last edited by lviggiani (2014-08-01 14:02:01)

Pse

Member

Registered: 2008-03-15

Posts: 413

Re: Laptop display brigthness always pushed to 100% when GDM starts

Yes, I noticed the same. It seems gdm sets the brightness to 100% right after logout, so when systemd-backlight records the current level, it is always at 100%. So, we probably need to look into how gdm handles brightness.

Last edited by Pse (2014-08-01 22:23:44)

mkoskar

Member

Registered: 2014-07-16

Posts: 64

Website

Re: Laptop display brigthness always pushed to 100% when GDM starts

I think this and https://bbs.archlinux.org/viewtopic.php?pid=1442710 are actually about same issue.

Pse

Member

Registered: 2008-03-15

Posts: 413

Re: Laptop display brigthness always pushed to 100% when GDM starts

@mkoskar, it looks similar, but there are a couple of differences:
- Using gdm here.
- Brightness goes to 100% after logging out of a user session (in the other topic the screen gets dimmer, not brighter).

The problem might be related, though.

Edit: I see your last post in the other topic talks about getting a brighter screen after logging out. In that case, yes, this may be the same problem.

Last edited by Pse (2014-08-02 01:37:00)

tumas

Member

Registered: 2012-02-08

Posts: 89

Re: Laptop display brigthness always pushed to 100% when GDM starts

https://bbs.archlinux.org/viewtopic.php?id=149316

This seems to be the same issue. The "solution" provided there still works; the only issue with this method is, that when you change the brightness-value afterwards it will jump to the highest level, because the gnome-brightness-control sill won't recognize the real brightness-level.

stricte

Member

Registered: 2010-01-20

Posts: 7

Re: Laptop display brigthness always pushed to 100% when GDM starts

This issue is related to xf86-video-intel or linux kernel (both have recent commits related with backlight). I have upgraded both: xf86-video-intel-git 2.99.914.63.g9b2cf5c-1 and linux-mainline 3.17rc1-1 and the problem disappeared.

Last edited by stricte (2014-08-22 17:13:31)