If cons_backlight_available is not set, cons_brightness will not be valid, return -1 to indicate so. same as WSDISPLAYIO_PARAM_BACKLIGHT.
If cons_backlight_available is not set, cons_brightness will not be valid,
return -1 to indicate so. same as WSDISPLAYIO_PARAM_BACKLIGHT.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars