Brightness/backlight sysfs knob does not work in 525.89.02 or 530.30.02


I have a Dell Precision 7760 with an A5000 used in discrete-only graphics mode. I can’t adjust the backlight brightness on this laptop by using /sys/class/backlight/nvidia_0/brightness (either write()ing ASCII decimal strings from 0 to 100 manually or by using xbacklight) when using the proprietary driver at version 525.89.02 or 530.30.02. This still works with 515.86.01, which I am now currently running again. I don’t have an nvidia-bug-report.log.gz to share. I can get and post one, if necessary, but switching graphics driver versions is inconvenient.