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#1 2011-02-07 20:35:34

CanadaRox
Member
Registered: 2006-08-06
Posts: 19

Dell L501x Screen Brightness

I've gotten most things working on my new laptop but I can't seem to figure out how to adjust my screen brightness.

The first thing I noticed was that there was no /proc/acpi/video directory.  So I searched for where it might be:

~ $ find / -iname *brightness* 2>/dev/null
/sys/devices/virtual/backlight/acpi_video0/brightness
/sys/devices/virtual/backlight/acpi_video0/actual_brightness
/sys/devices/virtual/backlight/acpi_video0/max_brightness
/sys/module/video/parameters/brightness_switch_enabled
/usr/lib/gegl-0.1/brightness-contrast.so
/usr/share/laptop-mode-tools/modules/lcd-brightness
/usr/share/gtk-doc/html/libgimpwidgets/stock-tool-brightness-contrast-16.png
/usr/share/gtk-doc/html/libgimpwidgets/stock-tool-brightness-contrast-22.png
/etc/laptop-mode/conf.d/lcd-brightness.conf

The first three seemed like they might be useful since they are similar to the ThinkPad brightness values here: https://wiki.archlinux.org/index.php/La … brightness.  Each one has only the number 15 in it.  When I try as root to do

echo -n X >/sys/devices/virtual/backlight/acpi_video0/brightness # X being replaced by any number from 0 to 15

I get:

bash: /sys/devices/virtual/backlight/acpi_video0/brightness: Permision denied

I have tried setting laptop-mode-tools to automatically echo different numbers when I unplug my laptop but they don't do anything.  If you might be able to point me in the right direction, or know how to change the brightness on the Dell L501x, I'd greatly appreciate the help.

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#2 2011-02-07 21:52:39

lagagnon
Member
From: an Island in the Pacific...
Registered: 2009-12-10
Posts: 1,087
Website

Re: Dell L501x Screen Brightness

It may or may not work but try "xbacklight", from the xorg-backlight package.


Philosophy is looking for a black cat in a dark room. Metaphysics is looking for a black cat in a dark room that isn't there. Religion is looking for a black cat in a dark room that isn't there and shouting "I found it!". Science is looking for a black cat in a dark room with a flashlight.

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#3 2011-02-07 22:14:17

CanadaRox
Member
Registered: 2006-08-06
Posts: 19

Re: Dell L501x Screen Brightness

I am able to change whatever xbacklight is reading from but no change with the actual screen brightness.

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#4 2011-02-08 15:51:25

Lothium
Member
Registered: 2009-10-10
Posts: 192

Re: Dell L501x Screen Brightness

Mmmh ...  I also have a Dell XPS Lx501 with the Nvidia GT 435M and KDE 4.6 and for me all works fine. I can use the keys on my keyboard or the battery plasmoid to change brightness.

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#5 2011-02-08 17:43:37

CanadaRox
Member
Registered: 2006-08-06
Posts: 19

Re: Dell L501x Screen Brightness

I think (read: guess) that Nvidia Optimus not working is somewhat related to this problem.  Would you happen to have an i7 in your laptop?  If you did that might explain why you are able to change the brightness (i7's don't have Optimus in the L501x).

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#6 2011-02-08 18:14:24

Lothium
Member
Registered: 2009-10-10
Posts: 192

Re: Dell L501x Screen Brightness

Yes exactly... I have the i7 and no integrated intel graphics... Sorry that I can't help you with this.

Just another thing: Do you get the synaptics touchpad work well? For me it works, but when I try to use two finger scroll, I can't use it when I lay my two fingers at the same time on the touchpad. I have to lay them one after another on the touchpad to use two finger scroll. Do you have the same problem or found a solution for this?

Best regards!

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#7 2011-02-08 19:17:42

CanadaRox
Member
Registered: 2006-08-06
Posts: 19

Re: Dell L501x Screen Brightness

I haven't enabled anything extra with the touchpad.  I've always used the side to scroll and that already works perfectly so I haven't touched anything other than disabling taps when typing.

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#8 2011-02-08 19:36:54

Lothium
Member
Registered: 2009-10-10
Posts: 192

Re: Dell L501x Screen Brightness

Ahh ok, I am not such a fan of the side scrolling, but this also works for me very good. But thanks for your answer!

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#9 2011-02-09 15:55:40

tinhtruong
Member
From: Australia
Registered: 2008-12-18
Posts: 117

Re: Dell L501x Screen Brightness

Lothium wrote:

Yes exactly... I have the i7 and no integrated intel graphics... Sorry that I can't help you with this.

Just another thing: Do you get the synaptics touchpad work well? For me it works, but when I try to use two finger scroll, I can't use it when I lay my two fingers at the same time on the touchpad. I have to lay them one after another on the touchpad to use two finger scroll. Do you have the same problem or found a solution for this?

Best regards!

I own a Dell L401X i7 with Nvidia GT 425m and my touchpad also has problem. I use gpointing-device-setting to enable two finger scrolling. Sometimes it worked pretty well, sometimes when I put two fingers on the touchpad, my mouse jumped all over the screen. I don't know why.
Another thing I notice with this laptop is that my touchpad lock key does not work anymore (it used to work with the fresh installation of Arch)

If you find the solution to these, please share!
PS: I don't why to hijack this thread of CanadaRox, I just want to share some problems some of you guys out there who is owning the same Dell laptop line.

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#10 2011-02-09 22:05:22

Lothium
Member
Registered: 2009-10-10
Posts: 192

Re: Dell L501x Screen Brightness

Sometimes I also get this jumping cursor and i read that this is a common problem. The touchpad lock key also doesn't work for me. If I find a solution, I write it down...

Best regards!

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#11 2011-02-16 10:59:45

Bogart
Member
From: Madrid, Spain
Registered: 2005-06-22
Posts: 272

Re: Dell L501x Screen Brightness

I have the Dell XPS L501X with core-i3 and Intel graphics (+ Nvidia optimus that doesn't work).

The screen brightness buttons don't work correctly, but I can adjust the brightness in two steps: First setting the brightness I want, either by "echo X > /sys/devices/virtual/backlight/acpi_video0/brightness" (where X is a number between 0 and 15) or by adjusting the slider in the battery monitor icon in the system tray. Any of those two things by themselves have no effect, but after changing them I press F4 and then the changes take effect (actually I changed in the BIOS the F numbers priority so I press Fn+F4).

For the touchpad I use synaptiks and have it configured to disable the touchpad when I plug in a mouse. That works great for me.

P.S: By the way, since I can't use the nVidia card (and don't want anyway), I blacklisted the nouveau module in /etc/rc.conf modules array. After doing it I think the laptop stays cooler and battery lasts a bit more. Anyone else tried and can confirm it makes a difference?

Last edited by Bogart (2011-02-16 11:31:07)

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#12 2011-02-17 20:09:56

CanadaRox
Member
Registered: 2006-08-06
Posts: 19

Re: Dell L501x Screen Brightness

If I su in I am able to change the brightness by doing: "echo X > /sys/devices/virtual/backlight/acpi_video0/brightness" then pressing Fn+F4 but the brightness changes to whatever I set, then on the next Fn+F4 (which is the lower brightness key) it returns to full brightness.  Fn + F5 (increase brightness doesn't do anything ever.  I guess I'll be stuck with changing both keys to the same code as F4, and write some sort of script that echo's (n +/- 1) to that file.

As for the nvidia graphics, just blacklisting nouveau isn't enough to prevent the GPU from being active.  You'll want to follow the instructions found here to disable it fully: https://lists.launchpad.net/hybrid-grap … 00450.html.  For me it reduced the battery usage from 2500 to 2000 (extending the battery life around an hour).

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#13 2011-02-19 17:24:23

Bogart
Member
From: Madrid, Spain
Registered: 2005-06-22
Posts: 272

Re: Dell L501x Screen Brightness

Yes, that's exactly the behavior I get. First set the number I want for brightness and then press Fn+F4 only once. If I press again it goes back to full brightness. For now it's enough, but obviously not a long term solution. I hope it will be fixed wit next kernel or whatever.

Thanks for the link about disabling the Nvidia GPU. I'll try it now and see how that works.

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#14 2011-03-13 23:13:08

epsilom
Member
Registered: 2009-04-18
Posts: 29

Re: Dell L501x Screen Brightness

I have Dell XPS 14 (L401x) and found ubuntu developer that work fix non-functional brightness control keys (https://launchpad.net/~kamalmostafa/+ar … gbacklight)

I made one package with these patchs: https://aur.archlinux.org/packages.php?ID=47386  and works for my, the keys brigthness work perfect, please test and tell me.

regards

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#15 2011-09-26 19:59:23

kasl33
Member
Registered: 2011-09-09
Posts: 13

Re: Dell L501x Screen Brightness

XPS L501X here with Nvidia GT435M and i7-Q740.

All media keys work fine and so does touchpad. The only problem is the touchpad disable/enable key (it disables, but doesn't re-enable).

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