From 62b693d7db46a2f0de2e00bcc733ee729ae37a20 Mon Sep 17 00:00:00 2001
From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Sun, 3 Nov 2002 01:37:08 +0000
Subject: [PATCH] Initialize d->bios_cyl. We know the media size in sectors,
 the number of heads end the number of sectors per track. If there's an
 obvious insanity (heads and sectors are both zero or the media size is not an
 integral multiple of heads times sector) we set the number of cylinders to
 zero.

---
 lib/libdisk/disk.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lib/libdisk/disk.c b/lib/libdisk/disk.c
index fe73d3e7d6ef..2a1b6aa2ecda 100644
--- a/lib/libdisk/disk.c
+++ b/lib/libdisk/disk.c
@@ -153,7 +153,7 @@ Int_Open_Disk(const char *name)
 	d->name = strdup(name);
 
 	a = strsep(&p, " ");	/* length in bytes */
-	o = strtoimax(a, &r, 0);
+	len = strtoimax(a, &r, 0);
 	if (*r) { printf("BARF %d <%d>\n", __LINE__, *r); exit (0); }
 
 	a = strsep(&p, " ");	/* sectorsize */
@@ -161,12 +161,11 @@ Int_Open_Disk(const char *name)
 	if (*r) { printf("BARF %d <%d>\n", __LINE__, *r); exit (0); }
 
 	d->sector_size = s;
+	len /= s;	/* media size in number of sectors. */
 
-	if (Add_Chunk(d, 0, o / s, name, whole, 0, 0, "-"))
+	if (Add_Chunk(d, 0, len, name, whole, 0, 0, "-"))
 		DPRINT(("Failed to add 'whole' chunk"));
 
-	len = o / s;
-
 	for (;;) {
 		a = strsep(&p, " ");
 		if (a == NULL)
@@ -182,6 +181,13 @@ Int_Open_Disk(const char *name)
 			printf("HUH ? <%s> <%s>\n", a, b);
 	}
 
+	/*
+	 * Calculate the number of cylinders this disk must have. If we have
+	 * an obvious insanity, we set the number of cyclinders to zero.
+	 */
+	o = d->bios_hd * d->bios_sect;
+	d->bios_cyl = (o != 0 && (len % o) == 0) ? len / o : 0;
+
 	p = q;
 	lo[0] = 0;