I can confirm this bug on several HP Probooks, including HP ProBook 4740s with Ubuntu 12.04.3 LTS (Precise) daily-live 2013-08-18 (from http://cdimage.ubuntu.com/precise/), which has Linux kernel 3.8 (tested with several linux-image-generic-lts-raring versions, including the latest - 3.8.0-29-generic)
Changing screen brighness works fine if I add boot parameter acpi_backlight=vendor in Ubuntu 12.04.3 LiveCD or installed system. Another workaround is to install older Linux kernel 3.5 from Ubuntu 12.04.2: sudo apt-get install linux-image-generic-lts-quantal So, problem is Btw, this HP Probook has 2 video chipsets: ubuntu@ubuntu:~$ lspci |grep -i VGA 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Thames [Radeon HD 7550M/7570M/7650M] I'm attachink /var/log/Xorg.0.log file when using 3.8.0-29-generic kernel (Ubuntu 12.04.3 LiveCD) ** Attachment added: "/var/log/Xorg.0.log file when using 3.8.0-29-generic kernel" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1208257/+attachment/3776767/+files/Xorg.0.log ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed ** Also affects: linux (Baltix) Importance: Undecided Status: New ** Summary changed: - [HP ProBook 4540s] brightness control problems + HP ProBook 4540s and 4740s brightness control problems -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1208257 Title: HP ProBook 4540s and 4740s brightness control problems To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1208257/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
