se quiser tentar eu resolvo o brilho sempre assim >
If your graphics is (for example) GFX0 (search it from ioreg), then you should find that device in dsdt. Under that device, there are other devices (usually LCD, CRT, TV...). Look for the device that has those methods (_BCM, _BCQ and _BCL) and then put Name (_HID, EisaId ("LCD1234")).
procuro o device com o _BCM, _BCQ e _BCL e coloco isso no começo dele Name (_HID, EisaId ("LCD1234") e tá resolvido.