From e76987f8c513aa5384eadcaef18ec260659d4113 Mon Sep 17 00:00:00 2001
From: briggs <briggs@openbsd.org>
Date: Mon, 21 Apr 1997 00:58:14 +0000
Subject: [PATCH] Take care when accessing DAFB--some quadra-class machines use
 other video controllers.

---
 sys/arch/mac68k/dev/grf_iv.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/sys/arch/mac68k/dev/grf_iv.c b/sys/arch/mac68k/dev/grf_iv.c
index 07a3d2943f6..8082cf0113c 100644
--- a/sys/arch/mac68k/dev/grf_iv.c
+++ b/sys/arch/mac68k/dev/grf_iv.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: grf_iv.c,v 1.14 1997/03/30 22:44:03 briggs Exp $	*/
+/*	$OpenBSD: grf_iv.c,v 1.15 1997/04/21 00:58:14 briggs Exp $	*/
 /*	$NetBSD: grf_iv.c,v 1.17 1997/02/20 00:23:27 scottr Exp $	*/
 
 /*
@@ -89,16 +89,25 @@ grfiv_match(parent, vcf, aux)
 	found = 1;
 
         switch (current_mac_model->class) {
-        case MACH_CLASSQ:
-        case MACH_CLASSQ2:
+	case MACH_CLASSQ:
+	case MACH_CLASSQ2:
 
-		/* Assume DAFB for all of these */
+		/*
+		 * Assume DAFB for all of these, unless we can't
+		 * access the memory.
+		 */
 
 		if (bus_space_map(oa->oa_tag, QUADRA_DAFB_BASE, 0x1000,
 					0, &bsh)) {
 			panic("failed to map space for DAFB regs.\n");
 		}
 
+		if (bus_probe(oa->oa_tag, bsh, 0x1C, 4) == 0) {
+			bus_space_unmap(oa->oa_tag, bsh, 0x1000);
+			found = 0;
+			goto nodafb;
+		}
+
 		sense = (bus_space_read_4(oa->oa_tag, bsh, 0x1C) & 7);
 
 		if (sense == 0)
@@ -121,6 +130,7 @@ grfiv_match(parent, vcf, aux)
 		break;
 
 	default:
+nodafb:
 		if (mac68k_vidlog == 0) {
 			found = 0;
 		}
-- 
2.20.1