On Tue, 17 Nov 2015, John Nemeth wrote:
http://nxr.netbsd.org/xref/src/sys/dev/acpi/acpi_display.c#1250 In other words, it is fully implemented, at least in -current.
Very cool, and come to think of it, it works like a champ on my -current laptop. So, I should have known it was already done.
Thanks, Swift