From 1a13286b104faeeb4f4bc3bfbf4d4fcdcd2569ed Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Mon, 23 Jul 2007 15:37:14 -0700
Subject: [PATCH] [x86 setup] APM: BX should be zero when disconnecting

For APM calls, BX contains the device index, which is zero for
the system BIOS.  Disconnect requres BX = 0.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
 arch/i386/boot/apm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/i386/boot/apm.c b/arch/i386/boot/apm.c
index 8be3f5686a..eab50c55a3 100644
--- a/arch/i386/boot/apm.c
+++ b/arch/i386/boot/apm.c
@@ -45,9 +45,10 @@ int query_apm_bios(void)
 
 	/* Disconnect first, just in case */
 	ax = 0x5304;
+	bx = 0;
 	asm volatile("pushl %%ebp ; int $0x15 ; popl %%ebp"
-		     : "+a" (ax)
-		     : : "ebx", "ecx", "edx", "esi", "edi");
+		     : "+a" (ax), "+b" (bx)
+		     : : "ecx", "edx", "esi", "edi");
 
 	/* Paranoia */
 	ebx = esi = 0;
-- 
2.39.5