Framebuffer device

Hello All,

I am using NetBSD 9.2 (amd64) with gop. My display driver is not
supported yet on the system (radeon r7 m265). Therefore I am using the
wsfb framebuffer device on my system. The screen is too bright for me.

Is it possible to adjust the screen brightness using the framebuffer
device? xrandr says "Gamma is set to 0", or "failed to get size of
gamma on output default".

Or is it possible to do this with the xf86 fbdev framebuffer, if we
can use that?

Regards,
Riza