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 Post subject: Backlight doesn't work with latest Maverick kernel
PostPosted: 09/12/2010, 0:57 
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Joined: 13/10/2010, 13:07
Posts: 4
Hi :)

Latest Maverick kernel, namely 2.6.35-24, prevents backlight control to work in my N150+ Samsung netbook.
I've manually modprobe'd the modules with debug=1 but I haven't noticed anything weird :?

To date, I've been using the modules installed with voRia kernels with latest Ubuntu kernels without problems.

Should I wait for the next voRia kernel or is there anything I can do to fix the issue? Right now I'm just booting with the voRia kernel, ignoring the kernel update.

Thanks!

Raúl


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 17/12/2010, 22:40 
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Joined: 01/05/2010, 8:16
Posts: 8
I have exactly the same problem for over a week on my N210 and the screen is now bleak.
Voria thank you if you could do something for us


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 20/12/2010, 15:56 
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Joined: 14/04/2010, 10:38
Posts: 7
Same problem for me.
No one of my attempts worked to solve so I just boot with the previous kernel.


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 21/12/2010, 15:21 
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Joined: 21/12/2010, 15:12
Posts: 12
Same problem on NF310. :(


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 21/12/2010, 16:40 
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Joined: 23/06/2010, 20:10
Posts: 5
Same problem on N220 and N150 :(

Regards


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 21/12/2010, 17:40 
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Joined: 21/12/2010, 15:12
Posts: 12
Just filed a bug report: https://bugs.launchpad.net/samsung-tools/+bug/693071
Did anybody discover source code for building samsung-backlight?


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 13:39 
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Joined: 21/12/2010, 15:12
Posts: 12
Adding
Code:
acpi_backlight=vendor

to the kernel's parameter list in your bootloader should do the trick.
For some reason, in 2.6.35-24 the ACPI driver starts feeling responsible for controlling the backlight.

In case of trouble when updating the kernel, backlight can also be controlled by manually writing numbers (0-7) to /sys/class/backlight/samsung/brightness (you may have to save several times to reach your target level of brightness).


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 13:47 
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Joined: 01/05/2010, 8:16
Posts: 8
Drake wrote:
Adding
Code:
acpi_backlight=vendor

to the kernel's parameter list in your bootloader should do the trick.
For some reason, in 2.6.35-24 the ACPI driver starts feeling responsible for controlling the backlight.

In case of trouble when updating the kernel, backlight can also be controlled by manually writing numbers (0-7) to /sys/class/backlight/samsung/brightness (you may have to save several times to reach your target level of brightness).
you know, for many peoples, it's more easy to install Windows ! ;D


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 22:26 
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Joined: 21/12/2010, 15:12
Posts: 12
I'm slightly aware of this fact.
Nevertheless, it might help some fanatic open source lover and Windows hater (I was told that Linux users sometimes match this character). ;)


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 22:34 
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Joined: 01/05/2010, 8:16
Posts: 8
sometimes yes .... but they are fewer and fewer ;D


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 22:58 
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Joined: 22/12/2010, 22:29
Posts: 1
Many many thanks Drake : ) works like a charm!

Here's how you change the kernel parameters. I am running Ubuntu 10.10 Netbook Edition on Samsung N210, so my bootloader is GRUB2.

Open the terminal...

1) Type "sudo nano /etc/default/grub" (replace nano with your favourite text editor, if needed)
2) Add "acpi_backlight=vendor" to the GRUB_CMDLINE_LINUX_DEFAULT parameters, so that...

GRUB_CMDLINE_LINUX_DEFAULT="quiet"

...or something similar becomes...

GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_backlight=vendor"

3) Close nano (CTRL+X) and save changes (Y)
4) Type "sudo update-grub2"
5) Type "sudo reboot"

In case you still have GRUB bootloader (instead of GRUB2), I believe you have to add "acpi_backlight=vendor" to /boot/grub/menu.lst, but unfortunately I don't have any system running with GRUB anywhere near, so I am unable to give you the full how-to. Google knows, I'm sure.


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 22/12/2010, 23:47 
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Joined: 01/05/2010, 8:16
Posts: 8
Thank you Drake and eth1cal for your "how to"...

but it doesn't work for me (N210 & classical ubuntu 10.10)
I will wait for again for few days and maybe make a downgrade toward ubuntu 10.04 LTS ;)


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 23/12/2010, 0:05 
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Joined: 21/12/2010, 15:12
Posts: 12
Try setting it manually:
1) Type
Code:
sudo nano /sys/class/backlight/samsung/brightness

=> The file should contain a single number (0-7).
2) Type a small number (replacing the old one), e.g. "1" and save several times (CTRL+O, ENTER).
=> Your screen should lower the brightness step by step.

Posting the output of the following command may also help to analyse your specific problem:
Code:
ls /sys/class/backlight


Before wearing sun glasses, try adjusting the brightness at the GRUB screen.


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 23/12/2010, 0:55 
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Joined: 01/05/2010, 8:16
Posts: 8
At the same time, an update of Voria's deposits, has changed for the maximum luminosity (and it's better for me for now)

As you suggest, I can manually adjust the brightness lower step by step without any problems. ;)

And here is the result of the code required:
acpi_video0 samsung


EDIT : I tried the eth1cal's method again and after the reboot, it works perfectly now, so a big thank you both for your help and your patience !


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 Post subject: Re: Backlight doesn't work with latest Maverick kernel
PostPosted: 23/12/2010, 1:49 
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Joined: 21/12/2010, 15:12
Posts: 12
The presence of the "acpi_video0" directory is a strong indication of the ACPI driver problem solved by the fix mentioned above. After adding "acpi_backlight=vendor" to your kernel's paramter list it must not (well, it should not) exist.
You might want to check if applying the parameter was successful by running
Code:
sudo dmesg | grep acpi_backlight

Output should look like
Code:
[0.000000] Command Line: ... quiet splash acpi_backlight=vendor
[0.000000] Kernel command line: ... quiet splash acpi_backlight=vendor

If there is no output, the parameter was not applied successfully. You may want to check the GRUB_CMDLINE_LINUX_DEFAULT string, rerun update-grub2 and reboot first.
If there is an output... well, one step at a time. Feel free to post it. :D

EDIT: I am glad to read about your success. :)


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