The workaround suggests that there's an interaction between the NVIDIA driver and another kernel module at play here. Presumably, adding the NVIDIA kernel modules to the initrd causes them to be loaded before the other module. Maybe video.ko, which registers its own brightness handler?
The modeswitch glitch should probably be tracked as a separate issue. Can somebody who is experiencing this glitch provide an example video? -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to nvidia-graphics-drivers-455 in Ubuntu. https://bugs.launchpad.net/bugs/1905591 Title: no brightness control in {455,460} after update from 450 Status in OEM Priority Project: New Status in nvidia-graphics-drivers-455 package in Ubuntu: Confirmed Status in nvidia-graphics-drivers-460 package in Ubuntu: Confirmed Bug description: On my Lenovo X1 Extreme with GPU: NVIDIA Corporation GP107M [GeForce GTX 1050 Ti Mobile]: WORKS FINE: nvidia-driver-450: 450.102.04-0ubuntu0.18.04.1 NO BRIGHTNESS CONTROL: nvidia-driver-455: 455.38-0ubuntu0.18.04.1 nvidia-driver-460: 460.32.03-0ubuntu0.18.04.1 nvidia-driver-460: 460.39-0ubuntu0.18.04.1 *WORKAROUND: See comment #11 (add nvidia drivers to initramfs). *Note that 460 fixes it for a 20.04 ThinkPad P73 per comment #6, but not for my 18.04.5 Lenovo ThinkPad X1 per comment #5. Updating to nvidia-driver-455 (or -460) results in loss of brightness control. On boot, the laptop display brightness is somewhat less than fully bright and cannot be changed. The brightness up/down keys do pop up the gnome gui brightness widget, and /sys/class/backlight/nvidia_0/* values do change, but the actual display's brightness does not. Problem occurs with either version of nvidia-driver-455 (the archive or the ~graphics-drivers/PPA) or any version of -460. Normal functionality returns if I downgrade to any version of nvidia- driver-450. Also observed: 455 and 460 temporarily display some pixel garbage while mode-switching during the graphic login sequence. Only a minor glitch, but note that 450 does not exhibit that issue either. Note also that manually applying this to /lib/systemd/system/nvidia-persistenced.service has no effect on the problem: https://github.com/hugh712/nvidia-graphics-drivers/commit/bccad5ee6444dd8c5c47ba19ea0232106a1086f5 Distributor ID: Ubuntu Description: Ubuntu 18.04.5 LTS Release: 18.04 Codename: bionic kernel: 5.4.0-54-generic #60~18.04.1-Ubuntu SMP Fri Nov 6 17:25:16 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/1905591/+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
