diff --git a/common/broxton/hw-gfx-gma-ddi_phy.ads b/common/broxton/hw-gfx-gma-ddi_phy.ads
index 89f19f0..51221b0 100644
--- a/common/broxton/hw-gfx-gma-ddi_phy.ads
+++ b/common/broxton/hw-gfx-gma-ddi_phy.ads
@@ -16,7 +16,9 @@
 
    type T is (BC, A);
 
-   procedure Power_On (Phy : T) is null;
-   procedure Power_Off (Phy : T) is null;
+   procedure Power_On (Phy : T);
+   procedure Power_Off (Phy : T);
+
+   subtype DDI_Phy_Port is GPU_Port range DIGI_A .. DIGI_C;
 
 end HW.GFX.GMA.DDI_Phy;