Can you really do that? AFAIU sysfs is now a de-facto uapi for backlights.
(answered to Javier's reply on this one)
With the sysfs interfaces disabled, who is going to trigger this code
except DRM?
AFAICT when the DRM connector updates the backlight status, backlight
runs this notifier only to call back into DRM to read back the value.
But the luminance property should already store that same value.
The systemd tools that read brightness could look at it (IE
brightnessctl). They wouldn't be able to write brightness but they can
look.
But yes you're right luminance property would store the same value.
