Created attachment 6825 Patch: Add radeon_bl0 to backlight_interfaces in src/xfpm-backlight-helper.c On my Thinkpad 11e, xfce is defaulting to use the thinkpad_screen backlight which doesn't work for me. The attached patch will put the radeon_bl0 backlight at higher priority, fixing the issue on my laptop. I'm not sure if this patch will adversely affect others.
Wow, well it's very hard to test if this will affect people negatively... I wonder if the only sensible way to expose this in a workaroundy yet usable way to users is a hidden xfconf option with which you can set a high-priority kernel interface.
This is no longer valid anyway: 36b2c96e91feeb118a4e8170c5d608795f00d5f2
Fixed in https://git.xfce.org/xfce/xfce4-power-manager/commit/?id=36b2c96e91feeb118a4e8170c5d608795f00d5f2