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Arsakes

Member

Registered: 2011-09-17

Posts: 27

[SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

I had Dell Precision 7510 with Ubuntu 14.04 preinstalled and backlight was working perfectly.
On could set it with Fn+F* combination and it had something like ~10 different brightness levels.

Now I've switched to arch and things aren't working properly.
I've tried following kernel options for backlight to work:

Case 1:

acpi_backlight=video

Effect:
Setting brightness with keys work the problem is each click changes brightness by "1" And you have to click many times to see difference.

$ls -l /sys/class/backlight/
acpi_video0

$cat /sys/class/backlight/acpi_video0/max_brightness
100

Somehow when brightness level is 100 the screen doesn't appear as bright as in case 2.

Case 2:

acpi_backlight=vendor

Effect:
Setting brightness with keys or through passing numbers into /sys/class/backligth/dell_backlight/brightness  doesn't work at all.

$ls -l /sys/class/backlight/
dell_backlight

$cat /sys/class/backlight/dell_backlight/max_brightness
15

Also the screen is brighter than even 100 on the case first.

Case 3:
Setting xorg option "EnableBrightnessControl" gives the same situation as in case 1.

It seems that Ubuntu somehow managed to use vendor drivers properly.

When I'm pressing Fn + F12/11 the key is recognized as 232 XF86MonBrightnessUp/XF86MonBrightnessDown

Last edited by Arsakes (2016-06-11 01:24:05)

jasonwryan

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From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

With option 1, does using xbacklight allow you to specify larger increments, eg.:

xbacklight -inc 10

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Arsakes

Member

Registered: 2011-09-17

Posts: 27

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Yes, and funny thing xbacklight seem to cover whole range of brightness (greater maximal brightness than in case 1 with manually clicking Fn+F12).
Furthermore xbacklight doesn't change the values in

/sys/class/backligh/acpi_video0/brightness
/sys/class/backligh/acpi_video0/actual_brightness

Should it be the case?
I really should backup whole Ubuntu configs.

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Cool. Write a simple script and bind it to your desired multimedia key (I do that with this).

In terms of how xbacklight interacts with /sys/: see https://wiki.archlinux.org/index.php/backlight

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Arsakes

Member

Registered: 2011-09-17

Posts: 27

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Thanks!

This is not an elegant solution however
I've read the article and didn't find any precise info about xbacklight interaction with /sys/

I wonder how is it possible that when I'm setting.

tee /sys/..../brightness <<< 100

manually, the brightness is lower than
xbacklight -set 100

(100 happens to be equal to max_brightness).

I will mark the thing closed and read more maybe.

What laptp do you have?

Last edited by Arsakes (2016-06-11 01:23:11)

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Well, it is elegant in an Arch Way. If you install all the packages Ubuntu does, then it would probably be a different story...

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Arsakes

Member

Registered: 2011-09-17

Posts: 27

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Hmm, is there any way I can make this work outside X?

EDIT:
Yes there using packages from aur.

Last edited by Arsakes (2016-06-11 09:51:51)

Arsakes

Member

Registered: 2011-09-17

Posts: 27

Re: [SOLVED - hacky] Dell Precision 7510 - backlight doesn't work

Ok, funny thing:

I've installed 

acpilight

from AUR to get stuff working in the console.
It seems that this version of acpilight doesn't increase the brightness correctly  - the maximal REAL brightness level is different for both of this utilities (xbacklight and acpilight).
Reallly strange beacuse the light level obtained from both utilties by get is the same.
Any ideas?

Last edited by Arsakes (2016-06-11 11:55:51)