There is a new patchset switches to use EDID-based DP quirk to list those DPCD
backlight panel.
I'll try verifying the new method and submit new SRU patches.
https://patchwork.kernel.org/cover/11376657/
** Changed in: linux-5.4 (Ubuntu Focal)
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1861521
Title:
[FOCAL][REGRESSION] Intel Gen 9 brightness cannot be controlled
Status in linux-5.4 package in Ubuntu:
In Progress
Status in linux-5.4 source package in Focal:
In Progress
Bug description:
After upgrading from Eoan (5.3.0-29.31) to Focal (5.4.0-12.15), I no
longer have the ability to control the backlight brightness on my HP
EliteBook 840 G5. When pressing the brightness hotkeys, the on-screen
indicator pops up and shows that the brightness setting is being
changed but the actual screen brightness is stuck on the lowest
setting.
This laptop has a built-in privacy screen. If I activate the privacy
screen (fn-f2), then the actual screen brightness goes to the maximum
setting and then I am able to dim and brighten the backlight as long
as the privacy screen functionality is turned on.
This is a regression from Eoan's 5.3.0-29.31 kernel where I was able
to control the brightness with and without the privacy screen
functionality being turned on.
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-12-generic 5.4.0-12.15
ProcVersionSignature: Ubuntu 5.4.0-12.15-generic 5.4.8
Uname: Linux 5.4.0-12-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Fri Jan 31 11:42:16 2020
InstallationDate: Installed on 2019-06-24 (221 days ago)
InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: linux-signed-5.4
UpgradeStatus: Upgraded to focal on 2020-01-28 (3 days ago)
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