Same bug (same workarounds) on ThinkPad T440s with current Trusty. ** Tags added: trusty
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1098216 Title: Regression in brightness control on Lenovo Thinkpad X230 (+tablet) and X1 Carbon Status in The Linux Kernel: In Progress Status in “linux” package in Ubuntu: Triaged Status in “linux” package in Fedora: Unknown 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". To manage notifications about this bug go to: https://bugs.launchpad.net/linux/+bug/1098216/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
