diff --git a/common/i945/hw-gfx-gma-gmch.ads b/common/i945/hw-gfx-gma-gmch.ads
new file mode 100644
index 0000000..740913e
--- /dev/null
+++ b/common/i945/hw-gfx-gma-gmch.ads
@@ -0,0 +1,27 @@
+--
+-- Copyright (C) 2026 Arthur Heymans <arthur@aheymans.xyz>
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; either version 2 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+
+with HW.GFX.GMA.Config;
+
+private package HW.GFX.GMA.GMCH is
+
+   GMCH_PORT_PIPE_SELECT_SHIFT : constant := 30;
+   GMCH_PORT_PIPE_SELECT_MASK  : constant := 1 * 2 ** 30;
+   type GMCH_PORT_PIPE_SELECT_Array is array (Pipe_Index) of Word32;
+   GMCH_PORT_PIPE_SELECT       : constant GMCH_PORT_PIPE_SELECT_Array :=
+     (Primary   => 0 * 2 ** GMCH_PORT_PIPE_SELECT_SHIFT,
+      Secondary => 1 * 2 ** GMCH_PORT_PIPE_SELECT_SHIFT,
+      Tertiary  => 0);
+
+end HW.GFX.GMA.GMCH;