This probably isn't a kernel issue. Backlight drivers generally only change the brightness when told to do so by userspace, although sometimes system firmware plays a role as well.
But based on the described behavior, I suspect that it was userspace setting the brightness value when the login screen appeared. gnome-settings-daemon is what will actually be applying the brightness settings, so I'm going to reassign the Linux task to that.
This probably isn't a kernel issue. Backlight drivers generally only change the brightness when told to do so by userspace, although sometimes system firmware plays a role as well.
But based on the described behavior, I suspect that it was userspace setting the brightness value when the login screen appeared. gnome-settings- daemon is what will actually be applying the brightness settings, so I'm going to reassign the Linux task to that.