I was asked to report this bug to the Intel driver Github: https://gitlab.freedesktop.org/drm/intel/-/issues/2794
I have also provided logs on this bug. This issue appears also on other projects, where it is not possible to use multiple same devices on a system because of this bug. Here an example: https://bugzilla.redhat.com/show_bug.cgi?id=1443678 The issue was not fixed back then. Some people made hotfixes by themselves: https://github.com/pruiz/aic94xx-hotfix ** Bug watch added: gitlab.freedesktop.org/drm/intel/-/issues #2794 https://gitlab.freedesktop.org/drm/intel/-/issues/2794 ** Bug watch added: Red Hat Bugzilla #1443678 https://bugzilla.redhat.com/show_bug.cgi?id=1443678 ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed -- 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: Confirmed 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 : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
