Brightness applet works in KDE but not in Gnome

[Vincent Arnoux]

Hello the list,
As the title says, I have in issue with the brightness applet in gnome
(the slider that lets you modify the screen brightness) on my 8.10
laptop. In KDE it works fine. In Gnome, when I move the slider, the
desktop will hang for a few minutes (5 to 10 minutes) and (very slow)
step by (very slow) step reach the brightness level I set. How can I
fix or at least where should I look to debug that behavior?

Thanks,
Vincent