Regression in brightness control on Lenovo Thinkpad X230 (+tablet) and X1 Carbon

Bug #1098216 reported by Stéphane Graber
340
This bug affects 78 people
Affects Status Importance Assigned to Milestone
Linux
Fix Released
Medium
linux (Fedora)
Fix Released
High
linux (Ubuntu)
Triaged
Medium
Seth Forshee

Bug Description

== Raring SRU Justification ==

Impact: A number of ThinkPad models have a workaround in the ACPI
backlight implementation for Windows 8 that more or less completely
breaks backlight control.

Fix: Add an OSI quirk to no longer claim to be Windows 8 on these
machines, causing the firmware to revert to the older, working behavior.

Test Case: Verified on LP #1098216 and bugzill.kernel.org #51231.

---

Something changed between the 3.5 and the 3.7 kernel, leading to broken brightness control on my Thinkpad x230.

Here are some test results:
== 3.5.0-21-generic ==
=== Post-boot values ===
/sys/class/backlight:
  - intel-backlight
    + actual_brightness => 4438
    + bl_power => 0
    + brightness => 4438
    + max_brightness => 4438
  - acpi_video0
    + actual_brightness => 15
    + bl_power => 0
    + brightness => 15
    + max_brightness => 15

=== Tests ===
echo 0 > acpi_video0/brightness => works
echo 0 > intel_backlight/brightness => works

== 3.8.0-0-generic ==
=== Post-boot values ===
/sys/class/backlight:
  - intel-backlight
    + actual_brightness => 4438
    + bl_power => 0
    + brightness => 4438
    + max_brightness => 4438
  - acpi_video0
    + actual_brightness => 100
    + bl_power => 0
    + brightness => 100
    + max_brightness => 100

=== Tests ===
echo 0 > acpi_video0/brightness => doesn't do anything
echo 0 > intel_backlight/brightness => works
---
ApportVersion: 2.8-0ubuntu1
Architecture: amd64
CheckboxSubmission: 12108b8b8b67d760cdd84f1b9574e7f3
CheckboxSystem: bb422ca46d02494cdbc459927a98bc2f
DistroRelease: Ubuntu 13.04
InstallationDate: Installed on 2012-09-02 (129 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120902)
MarkForUpload: True
Package: linux (not installed)
ProcEnviron:
 LANGUAGE=en_US:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 3.8.0-0.1-generic 3.8.0-rc3
Tags: raring
Uname: Linux 3.8.0-0-generic x86_64
UnreportableReason: The running kernel is not an Ubuntu kernel
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

WORKAROUND:

Add to /etc/default/grub
in the variable "GRUB_CMDLINE_LINUX_DEFAULT":

acpi_osi=\"!Windows 2012\"

e.g:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=\"!Windows 2012\""

Then run "sudo update-grub".

Revision history for this message
Brad Figg (brad-figg) wrote : Missing required logs.

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1098216

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu):
status: New → Incomplete
tags: added: quantal
Revision history for this message
Stéphane Graber (stgraber) wrote :
  • acpi Edit (1.8 KiB, application/binary)
tags: added: apport-collected raring
description: updated
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Stéphane Graber (stgraber) wrote :
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Stéphane Graber (stgraber) wrote :
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Stéphane Graber (stgraber) wrote :
  • fwts Edit (50 bytes, application/binary)
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Stéphane Graber (stgraber) wrote :
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Stéphane Graber (stgraber) wrote : Re: Regression in brightness control on Lenovo Thinkpad x230

Manually added everything listed on https://wiki.ubuntu.com/Kernel/Debugging/Backlight as apport doesn't appear to like my pre-release 3.8 kernel (from http://kernel.ubuntu.com/~rtg/Ubuntu-3.8.0-0.1/)

Revision history for this message
Joseph Salisbury (jsalisbury) wrote :

Do you happen to know the last good and first bad kernel versions? If so, I can perform a bisect to identify the commit that caused the regression.

If you don't know the first bad kernel, can you test the following kernels and report back? We are looking for the first kernel version that exhibits this bug:

v3.5.7: http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.5.7-quantal/
v3.6 final: http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.6-quantal/
v3.7-rc3: http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.7-rc3-raring/

You don't have to test every kernel, just up until the kernel that first has this bug.

Changed in linux (Ubuntu):
importance: Undecided → Medium
tags: added: performing-bisect
Revision history for this message
Stéphane Graber (stgraber) wrote :

Last 3.6 worked, first 3.7 didn't. Based on IRC discussion, that's because 3.7 now advertises win8 support in ACPI which triggers a change in the list of backlight values.

Changed in linux (Ubuntu):
status: Incomplete → Triaged
Revision history for this message
Stéphane Graber (stgraber) wrote :

For reference, the IRC discussion can be found at: http://irclogs.ubuntu.com/2013/01/10/%23ubuntu-kernel.html#t15:22

Revision history for this message
Seth Forshee (sforshee) wrote :

To summarize the root cause: If the OS reports itself as Windows 8, the firmware's _BCL returns a list of 101 brightness values, of which only 16 work. These 16 correspond to the values reported by _BCL if the OS does not claim to be Win8. Any brightness value passed to _BCM other than those 16 will be silently discarded without changing the brightness.

Changed in linux:
importance: Unknown → Medium
status: Unknown → Incomplete
Revision history for this message
Seth Forshee (sforshee) wrote :

I worked up a patch to disable Windows 8 compatibility on this machine (and the ThinkPad T430s as well since it was reported to have the same issue on the upstream bug report). A test build is available at:

http://people.canonical.com/~sforshee/lp1098216/linux-3.8.0-0.3~lp1098216v201301141657/

Changed in linux (Ubuntu):
assignee: nobody → Seth Forshee (sforshee)
status: Triaged → Incomplete
tags: removed: performing-bisect
Revision history for this message
Stéphane Graber (stgraber) wrote :

Test kernel works fine on the X230.

Changed in linux (Ubuntu):
status: Incomplete → Triaged
Revision history for this message
Daniel van Vugt (vanvugt) wrote : Re: Regression in brightness control on Lenovo Thinkpad X230 and X1 Carbon
summary: - Regression in brightness control on Lenovo Thinkpad x230
+ Regression in brightness control on Lenovo Thinkpad X230 and X1 Carbon
Revision history for this message
Anmar Oueja (anmar) wrote :

From bug #1121951 we found that the bug happens between 3.6 and 3.7-rc1 . Are we going to bisect this further to find out the offending code change?

Revision history for this message
Seth Forshee (sforshee) wrote :

We already know what the offending commit is.

commit a57f7f9175b8ccbc9df83ac13860488913115de4
Author: Bob Moore <email address hidden>
Date: Fri Aug 17 10:55:02 2012 +0800

    ACPICA: Add Windows8/Server2012 string for _OSI method.

The problem is that when Linux starts reporting itself as Windows 8 some Lenovo firmware changes its behavior to indicate that the ACPI backlight interface reports 101 brightness levels (this is a requirement of Windows 8). But in reality the firmware ignores 85% of the values that it says are valid and only accepts the same 16 values that it says are valid when the OS reports it self as something other than Windows 8. Any other values are completely ignored.

I've gone back and forth with upstream on this issue, but the maintainers haven't been very responsive. I've got a patch series that's been sitting on the mailing list for a couple of weeks now without any review from the maintainers.

Revision history for this message
Nathaniel Roach (nroach44) wrote :

This bug also effects the ThinkPad EDGE E330 - I'm compiling 3.8.3 with a modified patch now.

Revision history for this message
Seth Forshee (sforshee) wrote :

Nathaniel: If you'll run 'sudo acpidump > e330-acpi-tables.txt' and attach the resulting file I can check to verify that it really is the same problem.

1 comments hidden view all 309 comments
Revision history for this message
Nathaniel Roach (nroach44) wrote :

Seth: The attached modified patch stops the behavior, so I'd say it's the bug.

Result and patch attached anyway.

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Nathaniel Roach (nroach44) wrote :
tags: added: patch
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ZiNk (cserpentis) wrote :

Same thing on Lenovo Thinkpad T430. Think it's safe to assume it affects whole lenovo *30 line, since they use same bios/uefi implementation.

Revision history for this message
Seth Forshee (sforshee) wrote :

Nathaniel, your problem is fundamentally very similar but a little different. I suspect that if you boot without "!Windows 2012" you'll find some ACPI error messages in dmesg. I'd appreciate it if you could give this a try and then attach your dmesg so I can verify that this is correct.

Revision history for this message
Nathaniel Roach (nroach44) wrote :

Seth, I'm more of a power user, what would I need to do to test that?

Revision history for this message
Seth Forshee (sforshee) wrote :

Nathaniel: You need to boot to a kernel where your backlight doesn't work, i.e. no special kernel patches and no passing acpi_osi="!Windows 2012". Then try to adjust the backlight several times. After that run "dmesg > dmesg.txt" in a terminal and attach dmesg.txt.

Revision history for this message
Nathaniel Roach (nroach44) wrote :

So basically build a the same kernel sans patch and any extra arguments?

Building one now.

Revision history for this message
Seth Forshee (sforshee) wrote :

Or if you still have other kernels installed even easier would be to boot to a kernel with which you experienced the issue.

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Nathaniel Roach (nroach44) wrote :

Alright, here's the file.

Fresh extract of the tarball, but using the same config.

Revision history for this message
Seth Forshee (sforshee) wrote :

Nathaniel: You did try to change the brightness before collecting dmesg, and it did not change the brightness? I'm not seeing the errors I expected, though I'm confident they should occur because they happen when I load your ACPI tables into a debugger.

Maybe try poking some brightness values into the driver directly and see if you get any new messages at the bottom of dmesg. To do this, you'll first want to run 'cat /sys/class/backlight/acpi_video0/max_brightness'. This should output something like 101; if you get something much lower than that (like 15) then you still have acpi_osi="!Windows 2012" applied somehow.

Valid brightness values are anything from 0 to the value you get from the cat command. You set a value by running 'echo n > /sys/class/backlight/acpi_video0/brightness' as root, where n is a valid brightness value. Just be careful of going too low, you still want to be able to read the screen!

Seth Forshee (sforshee)
description: updated
description: updated
description: updated
summary: - Regression in brightness control on Lenovo Thinkpad X230 and X1 Carbon
+ Regression in brightness control on Lenovo Thinkpad X230 (+tablet) and
+ X1 Carbon
Brad Figg (brad-figg)
tags: added: verification-needed-raring
tags: added: verification-done
removed: verification-needed-raring
Changed in linux:
status: Incomplete → In Progress
Changed in linux:
status: In Progress → Incomplete
Changed in linux:
status: Incomplete → In Progress
229 comments hidden view all 309 comments
Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Created attachment 111591
dmidecode video.use_native_backlight -> not set

kernel 3.12.0-rc5 with patch_set_v5

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Created attachment 111601
kernel config, kernel 3.12.0-rc5 with patch_set_v5

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Thanks for your work on this Aaron! I've upgraded to kernel 3.12.0-rc5 and applied the patches. When I set video.use_native_backlight=1:

* everything works fine!
* /sys/class/backlight contains only intel_backlight
* there seem to be 21 brightness-levels available with gnome-power-manager
* the lowest level turns the backlight completely off (this doesn't happend with acpi_osi="!Windows 2012"), is this intentional?
* as already expected it is not longer possible to tune the brightness-level with the Fn+Keys, while working on a virtual-terminal
* thinkpad_acpi seem unhappy about the brightness-interface (see dmesg)

> thinkpad_acpi: http://ibm-acpi.sf.net/
> thinkpad_acpi: Unsupported brightness interface, please contact
> <email address hidden>

Looks good.

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Created attachment 111611
dmesg with complain from thinkpad_acpi about brightness interface

unsupported brightness interface

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In , TomWij (tomwij-linux-kernel-bugs) wrote :

Peter: Can you change this bug from NEEDINFO to UNCONFIRMED or CONFIRMED? I don't know for sure; but, due to the high traffic, the assigned person might miss your responses if the bug doesn't appear back in his list. It might be the possibility that only the assigned person can change, in which case never mind...

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Ohhhh. I thought the active developers change that if appropriate. I changed the status to VERIFIED, because there is no CONFIRMED available.

Revision history for this message
In , TomWij (tomwij-linux-kernel-bugs) wrote :

Eh, VERIFIED is usually a status to mark it resolved and verified by QA; you'll not want to pick that one, see https://bugzilla.kernel.org/page.cgi?id=fields.html#status for details on the various statuses.

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

The naming is pretty weird, isn't it? I don't have the canconfirm-permission. I hesitate to set this bug to "RESOLVED" but the description fits. Maybe Aaron would set this to IN_PROGRESS.

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

Thanks Peter for the test. If you show me your dmi info, I can add your system into a list so that the mentioned param will be automatically set for you.

Revision history for this message
In , tytso (tytso-linux-kernel-bugs) wrote :

I can confirm that I also need video.use_native_backlight=1 plus this patch (applied to 3.12-rc5) in order to make things work on my T430s laptop:

Handle 0x000F, DMI type 1, 27 bytes
System Information
        Manufacturer: LENOVO
        Product Name: 2352CTO
        Version: ThinkPad T430s
        Wake-up Type: Power Switch
        SKU Number: LENOVO_MT_2352
        Family: ThinkPad T430s

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

Created attachment 111821
Add Thinkpad T430s into the list

For Thinkpad T430s, apply on top of the existing v5 patchset.

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

(In reply to Aaron Lu from comment #152)
> Thanks Peter for the test. If you show me your dmi info, I can add your
> system into a list so that the mentioned param will be automatically set for
> you.

Theodore posted it in meanwhile :-)
You can find the complete output in comment 143. I will add the patch on top of v5 within the next days, but doesn't expect any surprise.

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Created attachment 112141
fixed typo, ThinkPad is written in camelCase, Thinkpad -> ThinkPad

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Created attachment 112151
fixed typo, Thinkpad -> ThinkPad

ThinkPad brand name is written in CamelCaseas, as reported by "dmidecode -t 1".

Revision history for this message
In , peter.weber (peter.weber-linux-kernel-bugs) wrote :

Great! I'm myself not able to type CamelCase without a typo. To be clear, is necessary to change it to "ThinkPad" to make it working!

By the way, let me be pedantic :-)
0003-ACPI-video-Do-not-register-backlight-if-win8-and-nat.patch
Line 54:
- * For Windows 8 systems: if set ture and the GPU driver has
+ * For Windows 8 systems: if set true and the GPU driver has

Thank you! Good night!

Revision history for this message
In , thirdwiggin (thirdwiggin-linux-kernel-bugs) wrote :

I tried the v5 patchset on 3.12.0-rc5 on my Lenovo Yoga 13, and video.use_native_backlight=1 also fixes the issue on this machine. I'm glad to help with any future testing needed to get this patch merged. Thanks for fixing this!

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

*** Bug 63811 has been marked as a duplicate of this bug. ***

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In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

*** Bug 67031 has been marked as a duplicate of this bug. ***

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

*** Bug 68751 has been marked as a duplicate of this bug. ***

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In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

*** Bug 62941 has been marked as a duplicate of this bug. ***

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In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

commit 1811fcb029fa3eca5bd1d25eab386b0c4b80fb93
Author: Aaron Lu <email address hidden>
Date: Tue Feb 18 13:54:20 2014 +0800

    ACPI / video: Add systems that should favour native backlight interface

has entered Rafael's linux-next tree.

Revision history for this message
In , fuffi.il.fuffo (fuffi.il.fuffo-linux-kernel-bugs) wrote :

Hi,
Thinkpad T430 here (without the s), I'm using linux 3.13.4 and systemd 208 from arch linux booting in bios mode with the last bios update (2.62).

The bug seems the same as for T430s and I can "fix" it with acpi_osi='!Windows 2012' or using video.use_native_backlight=1 as kernel command line in grub.

It works kinda well with video.use_native_backlight=1 except that I have now 4437 level of brightness in /sys/class/backlight/intel_backlight and as reported by Weber, systemd complains about this:

[ 9.226063] thinkpad_acpi: Unsupported brightness interface, please contact <email address hidden>

System Information
        Manufacturer: LENOVO
        Product Name: 2349KDG
        Version: ThinkPad T430
        (...)
        Wake-up Type: Power Switch
        SKU Number: LENOVO_MT_2349
        Family: ThinkPad T430

It is because of so many levels of backlight that I have in KDE this behavior switching brightness with the keys:
from 0 to 100: 0-10-20-30-40-50-60-70-80-90-100
from 100 to 0: 100-89-79-69...etc.

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

(In reply to edm from comment #165)
> Hi,
> Thinkpad T430 here (without the s), I'm using linux 3.13.4 and systemd 208
> from arch linux booting in bios mode with the last bios update (2.62).
>
> The bug seems the same as for T430s and I can "fix" it with
> acpi_osi='!Windows 2012' or using video.use_native_backlight=1 as kernel
> command line in grub.
>
> It works kinda well with video.use_native_backlight=1 except that I have now
> 4437 level of brightness in /sys/class/backlight/intel_backlight and as
> reported by Weber, systemd complains about this:
>
> [ 9.226063] thinkpad_acpi: Unsupported brightness interface, please
> contact <email address hidden>

This is harmless, I'll send a patch to fix this.

>
>
> System Information
> Manufacturer: LENOVO
> Product Name: 2349KDG
> Version: ThinkPad T430
> (...)
> Wake-up Type: Power Switch
> SKU Number: LENOVO_MT_2349
> Family: ThinkPad T430
>
> It is because of so many levels of backlight that I have in KDE this
> behavior switching brightness with the keys:
> from 0 to 100: 0-10-20-30-40-50-60-70-80-90-100
> from 100 to 0: 100-89-79-69...etc.

I'll prepare a new patch for your laptop later(together with some other model once that model is confirmed to work well with video.use_native_backlight=1).

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

commit 0e9f81d3b7cd0649a3bc437391b6a0650f98f844
Author: Aaron Lu <email address hidden>
Date: Tue Feb 18 13:54:20 2014 +0800

    ACPI / video: Add systems that should favour native backlight interface

entered Linus' tree as v3.14 material.

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

BTW, edm, please also attach your acpidump here, thanks.

Revision history for this message
In , fuffi.il.fuffo (fuffi.il.fuffo-linux-kernel-bugs) wrote :

Created attachment 127991
acpidump T430

Output of
# acpidump > acpidump-T430.txt

Revision history for this message
In , fuffi.il.fuffo (fuffi.il.fuffo-linux-kernel-bugs) wrote :

Just a stupid question: does it make any difference doing "acpidump" with or without acpi_osi="!Windows 2012" as boot option?

Francois Thirioux (fthx)
tags: added: trusty
Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

(In reply to edm from comment #170)
> Just a stupid question: does it make any difference doing "acpidump" with or
> without acpi_osi="!Windows 2012" as boot option?

No difference.
I'll add your system into the table shortly, sorry for the long delay.

Revision history for this message
In , lyude (lyude-linux-kernel-bugs) wrote :

Created attachment 131691
acpi dump for ThinkPad Helix (UEFI)

Revision history for this message
In , lyude (lyude-linux-kernel-bugs) wrote :

Created attachment 131701
dmidecode dump for ThinkPad Helix

That should be all the information you need on the Helix regarding the patch I submitted ( https://patchwork.kernel.org/patch/3938911/ ), let me know if you need anything else

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

(In reply to Aaron Lu from comment #171)
> (In reply to edm from comment #170)
> > Just a stupid question: does it make any difference doing "acpidump" with
> or
> > without acpi_osi="!Windows 2012" as boot option?
>
> No difference.
> I'll add your system into the table shortly, sorry for the long delay.

Matthew sent out a patch to enable native backlight control interface by default for win8 systems so that we do not need to add more systems into the DMI table:
http://www.spinics.net/lists/dri-devel/msg57228.html

Revision history for this message
In , gabriele.mzt (gabriele.mzt-linux-kernel-bugs) wrote :

Created attachment 137791
Dell XPS13 9333 acpidump

I attached the acpidump of my Dell XPS13 9333.

If video.use_native_backlight=1 is not added to the kernel cmdline, the Fn keys are buggy: the brightness increases or decreases by one unit (max_brigthness is 937, so a variation of 1 is hardly noticeable) and I get not DE OSD.

With video.use_native_backlight=1, I get the OSD and a brightness variations of 10% as expected.

System Information
        Manufacturer: Dell Inc.
        Product Name: XPS13 9333

Revision history for this message
In , robert.zavalczki (robert.zavalczki-linux-kernel-bugs) wrote :

Created attachment 140631
ThinkPad T530 use native backlight patch

Revision history for this message
In , robert.zavalczki (robert.zavalczki-linux-kernel-bugs) wrote :

The backlight keys do not work properly with kernel 3.15.1 and ThinkPad T530 (with Intel integrated graphics). Only 2 brightness levels are available.

I noticed that using native backlight option for Thinkpad T530 fixes the issue:

see attachment 140631

After applying the above patch 11 brightness levels + blank can be set (I am using an Xfce 4.10 desktop).

Weirdly, in pre 3.15 kernel versions adding the use native backlight option caused my monitor to become unresponsive (stay blank) after a screen lock followed by a suspend screen. I no longer get that behavior with kernel version 3.15.1. Should you need any more information I can happily provide it.

Revision history for this message
In , corsac (corsac-linux-kernel-bugs) wrote :

So I just got the 3.16 kernel with the changes for all Windows 8 laptops.

And while I bought this laptop (Thinkpad x201s) in 2010, it seems a BIOS update added the “support” for Windows 8 (at least that's a guess from http://paste.debian.net/120230/ , I can provide full acpidump).

So this laptop where brightness keys where working perfectly using ACPI, has now the same issue, and I need to have something in userspace doing the job.

That's really a regression for me.

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

Hi Perez,

I believe commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d is meant to fix such problems:

commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d
Author: Hans de Goede <email address hidden>
Date: Thu Aug 28 10:20:46 2014 +0200

    ACPI / video: Add a disable_native_backlight quirk

    Some laptops have a working acpi_video backlight control, and using native
    backlight on these causes a regression where backlight control does not work
    when userspace is not handling brightness key events. Disable native_backlight
    on these to fix this.

    Link: https://bugzilla.kernel.org/show_bug.cgi?id=81691
    Reported-and-tested-by: Andre Müller <email address hidden>
    Cc: 3.16+ <email address hidden> # 3.16+
    Signed-off-by: Hans de Goede <email address hidden>
    Signed-off-by: Rafael J. Wysocki <email address hidden>

Feel free to submit a patch to add your model into the video_dmi_table to disable native backlight control.

Revision history for this message
In , corsac (corsac-linux-kernel-bugs) wrote :

(In reply to Aaron Lu from comment #179)
> Hi Perez,
>
> I believe commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d is meant to fix
> such problems:
>
> commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d
> Author: Hans de Goede <email address hidden>
> Date: Thu Aug 28 10:20:46 2014 +0200
>
> ACPI / video: Add a disable_native_backlight quirk
>
> Some laptops have a working acpi_video backlight control, and using
> native
> backlight on these causes a regression where backlight control does not
> work
> when userspace is not handling brightness key events. Disable
> native_backlight
> on these to fix this.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=81691
> Reported-and-tested-by: Andre Müller <email address hidden>
> Cc: 3.16+ <email address hidden> # 3.16+
> Signed-off-by: Hans de Goede <email address hidden>
> Signed-off-by: Rafael J. Wysocki <email address hidden>
>
> Feel free to submit a patch to add your model into the video_dmi_table to
> disable native backlight control.

Thanks. So the “DMI table” approach was considered bad because not sustainable for this bug, but ok for bug #81691 ?

Anyway, will provide the correct DMI information on that bug.

Revision history for this message
In , aaron.lu (aaron.lu-linux-kernel-bugs) wrote :

(In reply to Yves-Alexis Perez from comment #180)
> (In reply to Aaron Lu from comment #179)
> > Hi Perez,
> >
> > I believe commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d is meant to fix
> > such problems:
> >
> > commit 5f24079b021cd3147c8d24ba65833f7a0df7e80d
> > Author: Hans de Goede <email address hidden>
> > Date: Thu Aug 28 10:20:46 2014 +0200
> >
> > ACPI / video: Add a disable_native_backlight quirk
> >
> > Some laptops have a working acpi_video backlight control, and using
> > native
> > backlight on these causes a regression where backlight control does not
> > work
> > when userspace is not handling brightness key events. Disable
> > native_backlight
> > on these to fix this.
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=81691
> > Reported-and-tested-by: Andre Müller <email address hidden>
> > Cc: 3.16+ <email address hidden> # 3.16+
> > Signed-off-by: Hans de Goede <email address hidden>
> > Signed-off-by: Rafael J. Wysocki <email address hidden>
> >
> > Feel free to submit a patch to add your model into the video_dmi_table to
> > disable native backlight control.
>
> Thanks. So the “DMI table” approach was considered bad because not
> sustainable for this bug, but ok for bug #81691 ?

The systems that claim to be Win8 but have a working ACPI video interface are supposed to be not common(hopefully this is true), so should be OK to keep a DMI table for them. While the systems that claim to be Win8 and don't have a working ACPI video interface are supposed to be the common case, so keeping a DMI table for all of them is not feasible.

>
> Anyway, will provide the correct DMI information on that bug.

OK, thanks.

Changed in linux (Fedora):
importance: Unknown → High
status: Unknown → Fix Released
Changed in linux:
status: In Progress → Fix Released
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