This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:
apport-collect 1903841 and then change the status of the bug to 'Confirmed'. If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'. This change has been made by an automated script, maintained by the Ubuntu Kernel Team. ** Changed in: linux (Ubuntu) Status: New => Incomplete -- 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/1903841 Title: i915 kerner driver can't initialize two connected LVDS outputs Status in linux package in Ubuntu: Incomplete Status in Debian: Incomplete Bug description: The bug appears from Ubuntu 18.04 and persists in Ubuntu 20.04 and 20.10. The hardware: 00:02.0 VGA compatible controller: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display (rev 11) The bug appears only if both LVDS-Outputs are connected to TFT panels at the same time. 3) Expected (works at Ubuntu 16.04): The graphic card is properly initialized and the intel_backlight links appear: ll /sys/class/backlight/ lrwxrwxrwx 1 root root 0 Feb 11 2016 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/ lrwxrwxrwx 1 root root 0 Feb 11 2016 intel_backlight ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-2/intel_backlight/ Both TFT panels connected via LVDS are on and are showing the desktop. 4) What happens instead: The the initialisation of the graphic card by the i915 kernel driver fails: dmesg | grep dup [ 2.951765] sysfs: cannot create duplicate filename '/class/backlight/intel_backlight' [ 2.951792] sysfs_warn_dup.cold+0x17/0x35 The /sys/class/backlight/ directory is empty. Modesetting fails: xrandr shows only one eDP-1 output and the disconnected outputs HDMI-1 and VGA-1 are gone. The TFT-Panels are off. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1903841/+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