Apply by doing:
	cd /usr/src
	patch -p0 < 013_brooktree.patch

And then rebuild your kernel.

Index: sys/dev/pci/brooktree848.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/brooktree848.c,v
retrieving revision 1.7
diff -u -r1.7 brooktree848.c
--- sys/dev/pci/brooktree848.c	1999/02/19 02:54:38	1.7
+++ sys/dev/pci/brooktree848.c	1999/11/14 01:59:56
@@ -1,4 +1,4 @@
-/*	$OpenBSD: brooktree848.c,v 1.7 1999/02/19 02:54:38 deraadt Exp $	*/
+/* $OpenBSD: brooktree848.c,v 1.12 1999/10/31 20:50:04 deraadt Exp $ */
 /* $FreeBSD: brooktree848.c,v 1.64 1999/01/28 17:47:47 roger Exp $ */
 /* BT848 Driver for Brooktree's Bt848, Bt849, Bt878 and Bt 879 based cards.
    The Brooktree  BT848 Driver driver is based upon Mark Tinguely and
@@ -1939,14 +1939,15 @@
 	int		unit;
 
 	unit = UNIT( minor(dev) );
-	if (unit >= NBKTR)			/* unit out of range */
+	if (unit >= NBKTR || unit > bktr_cd.cd_ndevs)	/* unit out of range */
 		return( ENXIO );
 
-#if defined(__NetBSD__) || defined(__OpenBSD__)
+	if (bktr_cd.cd_devs == NULL)
+		return( ENXIO );
+
 	bktr = bktr_cd.cd_devs[unit];
-#else
-	bktr = &(brooktree[ unit ]);
-#endif
+	if (bktr == NULL)
+		return ( ENXIO );
 
 	if (!(bktr->flags & METEOR_INITALIZED)) /* device not found */
 		return( ENXIO );	
