Screen brightness does not work properly on samsung chronos 7

[Onlinelli]

Neither the brighness keys nor the system settings diaglog allowed me to change the screen brightness on my samsung chronos 7;

only after removing " acpi_backlight=vendor" from grub it worked flawlessly.....

reported on samsung np700z on 13.04 (testing), all current updates.

[Chris Wilson (ickle)]

Why was acpi_backlight=vendor on your command line?

[Onlinelli (cornelius-maihoefer)]

It came with the kernel update.

2013/2/11 Chris Wilson <email address hidden>

> Why was acpi_backlight=vendor on your command line?
>
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> You received this bug notification because you are subscribed to the bug
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> https://bugs.launchpad.net/bugs/1104529
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> Title:
> Screen brightness does not work properly on samsung chronos 7
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[Chris Wilson (ickle)]

For reference, can you please paste the output of

grep 'backlight control interface' /var/log/Xorg.0.log

with and without acpi_backlight=vendor

[Luis Sanjuán (luisj-sanjuan)]

FWIW

Mine is a different Samsung machine (NP900x3d), my Ubuntu version is 12.10. I've tried with/without acpi_backlight=vendor .

More precisely this is my current boot command line:

luis@sams9:~$ cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.5.0-26-generic root=... ro quiet splash i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1 vt.handoff=7

(The i915* options are my own customizations)

The output:

* with acpi_backlight=vendor added (Fn key combination does not work):

[ 5.613] (--) intel(0): found backlight control interface /sys/class/backlight/samsung

* without acpi_backlight=vendor, as it is in the referred /proc/cmdline (Fn key combination works):

[ 5.097] (--) intel(0): found backlight control interface /sys/class/backlight/acpi_video0

The weird thing is that acpi_backlight=verdor worked when BIOS was in UEFI mode. I've changed this to CSM mode after some research about the infamous firmware bug:

http://mjg59.dreamwidth.org/22855.html

Unfortunately I cannot provide more info for the UEFI mode.

The main advantage of using the samsung interface is that the minimum brightness threshold is lesser than in the native acpi_video interface, the former allows to dim completely the screen with the corresponding gaining in power saving.

[penalvch (penalvch)]

Onlinelli, this bug was reported a while ago and there hasn't been any activity in it recently. We were wondering if this is still an issue? If so, could you please test for this with the latest development release of Ubuntu? ISO images are available from http://cdimage.ubuntu.com/daily-live/current/ .

If it remains an issue, could you please run the following command in the development release from a Terminal (Applications->Accessories->Terminal), as it will automatically gather and attach updated debug information to this report:

apport-collect -p linux REPLACE-WITH-BUG-NUMBER

If reproducible, could you also please test the latest upstream kernel available (not the daily folder) following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags:
kernel-fixed-upstream
kernel-fixed-upstream-VERSION-NUMBER

where VERSION-NUMBER is the version number of the kernel you tested. For example:
kernel-fixed-upstream-v3.13-rc7

This can be done by clicking on the yellow circle with a black pencil icon next to the word Tags located at the bottom of the bug description. As well, please remove the tag:
needs-upstream-testing

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-VERSION-NUMBER

As well, please remove the tag:
needs-upstream-testing

Once testing of the upstream kernel is complete, please mark this bug's Status as Confirmed. Please let us know your results. Thank you for your understanding.

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]