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[Bug 1261853] Re: 8086:0166 [Dell Inspiron 15R 5521] Impossible to adjust the screen backlight


Alex Barattini, thank you for advising on the potential fix commit. Regarding it http://www.spinics.net/lists/linux-acpi/msg47755.html , in order to test this patch, start by copying from the line where it notes:
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c

to the last code line before the double dash:
 static int register_count;

Your patch file should be exactly as shown, honoring all spaces, or lack thereof:
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 995e91b..b3032f8 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -85,7 +85,7 @@ module_param(allow_duplicates, bool, 0644);
  * For Windows 8 systems: if set ture and the GPU driver has
  * registered a backlight interface, skip registering ACPI video's.
-static bool use_native_backlight = false;
+static bool use_native_backlight = true;
 module_param(use_native_backlight, bool, 0644);
 static int register_count;

save this file to your Desktop as testfix.patch. Then execute at a terminal:
git config --global user.email "you@xxxxxxxxxxx" && git config --global user.name "Your Name" && git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git ~/Desktop/linux-stable && patch ~/Desktop/linux-stable/drivers/acpi/video.c ~/Desktop/testfix.patch && git add . && git commit

Now in the new window type:

press Ctrl+O -> Enter -> Ctrl+X. Then, type at a terminal:
git log -n 1 | grep commit

which should post the commit:
commit <COMMIT>

Use this commit in the below terminal command:
git checkout <COMMIT> && cp /boot/config-`uname -r` .config && yes '' | make oldconfig && make-kpkg clean && CONCURRENCY_LEVEL=`getconf _NPROCESSORS_ONLN` fakeroot make-kpkg --initrd --append-to-version=-custom2 kernel_image kernel_headers && cd .. && sudo dpkg -i *.deb

If for whatever reason the new kernel doesn't boot, it may not be you
did something wrong, but just that it won't boot with this commit.

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  8086:0166 [Dell Inspiron 15R 5521] Impossible to adjust the screen

Status in “linux” package in Ubuntu:

Bug description:
  the change in the level of illumination of the screen, through the
  corresponding option in the control panel, has no effect.

  WORKAROUND: Works only with Ubuntu kernel version 3.11.0-14-generic, as in the v.3.13-rc3 produces black screen:

  Upstream post: http://www.spinics.net/lists/linux-acpi/msg48075.html

  ProblemType: Bug
  DistroRelease: Ubuntu 13.10
  Package: linux-image-3.11.0-14-generic 3.11.0-14.21
  ProcVersionSignature: Ubuntu 3.11.0-14.21-generic 3.11.7
  Uname: Linux 3.11.0-14-generic x86_64
  ApportVersion: 2.12.5-0ubuntu2.1
  Architecture: amd64
   /dev/snd/controlC0:  alex       1443 F.... pulseaudio
                        alex      11159 F.... pulseaudio
  Date: Tue Dec 17 18:50:13 2013
  HibernationDevice: RESUME=UUID=04335018-6e1d-453d-a8ba-25ae1c34f2eb
  InstallationDate: Installed on 2013-12-14 (2 days ago)
  InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
  MachineType: Dell Inc. Inspiron 5521
  MarkForUpload: True
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-14-generic.efi.signed root=UUID=d4cdcfba-0a53-41d0-a9ce-0516d3fab0f0 ro quiet splash vt.handoff=7
   linux-restricted-modules-3.11.0-14-generic N/A
   linux-backports-modules-3.11.0-14-generic  N/A
   linux-firmware                             1.116
  SourcePackage: linux
  StagingDrivers: rts5139
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 02/22/2013
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A06
  dmi.board.name: 0K08H3
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: A06
  dmi.modalias: dmi:bvnDellInc.:bvrA06:bd02/22/2013:svnDellInc.:pnInspiron5521:pvrA06:rvnDellInc.:rn0K08H3:rvrA00:cvnDellInc.:ct8:cvrA06:
  dmi.product.name: Inspiron 5521
  dmi.product.version: A06
  dmi.sys.vendor: Dell Inc.

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