Created attachment 168187 [details]
2012 Macbook Air (Sandybridge)
Brightness is set to 0 when loading i915kms from console with kldload.
Blindly (or via ssh) typing intel_backlight 80 restores brightness.
Setting hw.acpi.video.lcd0.fullpower = some value in loader.conf does not help.
I can confirm this behavior when booted using BIOS mode. VT works fine after KMS is loaded using EFI mode. I can confirm this with nvidia-modeset, and radeomkms as well. All work fine when using EFI.
I think this may be related to: