** Description changed: + [Impact] + After Ubuntu-5.4.0-9.12 which introduce DPCD backlight patches, the + backlight control on some platforms fail to work. + It seems using OUI string to map the panels which support DPCD + backlight doesn't work well, it mis-mapped those panel that doesn't + support DPCD backlight, and breaks the backlight control. + + [Fix] + The author of the origin DPCD backlight patches recently provides a + DP quirks based on EDID identification. + + [Fix] + Verified on the machine with DPCD backlight and also on the machine + which has regression with the OUI quirks, both of them work now. + + [Regression Potential] + Low, it introduce a new quirks to list the panels which support DPCD + backlight. + + =============================== + 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 + 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)
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1861521 Title: [FOCAL][REGRESSION] Intel Gen 9 brightness cannot be controlled To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-5.4/+bug/1861521/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
