Re: Bug Report - [Acer Aspire V5-122P] Unable to adjust screen brightness

Lewis Toohey
2014-05-26T12:19:03Z

On 26 May 2014 06:48, Aaron Lu <aaron.lu@intel.com> wrote:
> On 05/26/2014 04:42 AM, Lewis Toohey wrote:
>> On 23 May 2014 13:50, Hans de Goede <hdegoede@redhat.com> wrote:
>>> Hi Lewis et all,
>>>
>>> On 05/23/2014 02:07 PM, Lewis Toohey wrote:
>>>> On 23 May 2014 02:34, Aaron Lu <aaron.lu@intel.com> wrote:
>>>>> On 05/21/2014 09:02 PM, Lewis Toohey wrote:
>>>>>> Hi Aaron
>>>>>>
>>>>>> I followed your instructions and can report some limited success. I
>>>>>> have two interfaces listed in /sys/class/backlight namely:
>>>>>> acpi_video0 radeon_bl0
>>>>>>
>>>>>> max_brightness for acpi_video0 is 11. Echo-ing new values to
>>>>>> brightness appears to have no effect.
>>>>>>
>>>>>> max_brightness for radeon_bl0 is 255. Echo-ing new values to
>>>>>> brightness does adjust the screen brightness as you would expect.
>>>>>>
>>>>>> Results are the same on both battery and powered.
>>>>>>
>>>>>> I hope that is useful.
>>>>>
>>>>> I think Hans' patchset should solve your problem, can you please give it
>>>>> a try? You will need to pass the video.use_native_backlight=1 to kernel
>>>>> cmdline when testing, thanks.
>>>>>
>>>>> [PATCH resend 0/4] Make video.use_native_backlight=1 work properly with nouveau
>>>>> http://www.spinics.net/lists/dri-devel/msg59941.html
>>>>>
>>>>> -Aaron
>>>>
>>>> Aaron
>>>>
>>>> Thank you for this. Unfortunately I am going to have to ask you for a
>>>> bit of help here as I am now, officially, "out of my depth". I
>>>> appreciate this is a pain as you will have to take time explaining it
>>>> to me and I apologise for that.
>>>>
>>>> I have figured out how to pass the kernel command line argument, this
>>>> is not an issue.
>>>>
>>>> I have located the patch you refer to here:
>>>> https://bugzilla.redhat.com/attachment.cgi?id=894577
>>>> (which I believe is correct) but I cannot figure out how to apply it.
>>>
>>> That is not the right patch, you need a set of 2 patches. I've attached
>>> them to this mail. Note please ignore the numbering starting at 6, these
>>> are the 2 patches you need. You will need to build a Linux kernel with
>>> these 2 patches applied, see your distributions documentation on how
>>> to build a kernel from source.
>>>
>>> I don't know which distro you are using, I've a Fedora kernel with this
>>> patches included available here:
>>>
>>> http://people.fedoraproject.org/~jwrdegoede/rhbz1093171/
>>>
>>> Regards,
>>>
>>> Hans
>>
>> Hans
>>
>> Unfortunately I am unable to apply these patches against the latest
>> mainline kernel. I get two fails when applying the second patch file
>> and then the kernel will not compile. Please see output information
>> below.
>
> I've prepared a git branch for you:
> https://github.com/aaronlu/linux.git for-lewis
>
> It's based on Rafael's linux-next plus Hans' patch 2 and 3.
>
> Thanks,
> Aaron
>
>>
>> Can you advise?
>>
>> Many thanks
>>
>> ===APPLYING PATCHES TO LATEST MAINLINE KERNEL====
>>
>> lewis@HappyFunMeaowMeaow:~/KernelTesting/Kernel/linux$ patch -p1 <
>> 0006-backlight-Add-backlight-device-un-registration-notif.patch
>> (Stripping trailing CRs from patch; use --binary to disable.)
>> patching file drivers/video/backlight/backlight.c
>> (Stripping trailing CRs from patch; use --binary to disable.)
>> patching file include/linux/backlight.h
>> lewis@HappyFunMeaowMeaow:~/KernelTesting/Kernel/linux$ patch -p1 <
>> 0007-acpi-video-Unregister-the-backlight-device-if-a-raw-.patch
>> (Stripping trailing CRs from patch; use --binary to disable.)
>> patching file drivers/acpi/video.c
>> Hunk #1 FAILED at 151.
>> Hunk #2 succeeded at 161 (offset -1 lines).
>> Hunk #3 FAILED at 1837.
>> Hunk #4 succeeded at 1868 (offset -113 lines).
>> Hunk #5 succeeded at 1999 (offset -113 lines).
>> Hunk #6 succeeded at 2023 (offset -113 lines).
>> 2 out of 6 hunks FAILED -- saving rejects to file drivers/acpi/video.c.rej
>>
>>
>> ==LAST LINES OF BUILD BEFORE FAIL===
>>
>> CC [M] fs/xfs/xfs_ioctl32.o
>> LD [M] fs/xfs/xfs.o
>> make[1]: Leaving directory `/home/lewis/KernelTesting/Kernel/linux'
>> make: *** [debian/stamp/build/kernel] Error 2
>> lewis@HappyFunMeaowMeaow:~/KernelTesting/Kernel/linux$
>>
>>
>

Aaron

Many thanks for this. I can confirm that booting with this kernel and
passing the video.use_native_backlight = 1 argument means that the
backlight works perfectly on my laptop (both using the keyboard hot
keys and the gnome/unity settings applet).

I'll post to the ubuntu launchpad page later with instructions for
other people to do this. I assume its presence in the linux-next tree
means that it will be fixed in an upcoming kernel release? (sorry, I
don't know quite how the process works).

If I can provide more information or do some more useful testing
please do not hesitate to let me know.

Thank you both for your help - really appreciated.