From e9601c59e62abc17c79e6e8b205595b944dc6e09 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Thu, 31 May 2007 15:53:37 -0700
Subject: [PATCH] If no serial console is configured, don't bother calling into
 it

If there is no serial console configured, we can simply drop writes
from com32 rather than letting syslinux do that.
---
 com32/lib/sys/serial_write.c  | 4 ++++
 com32/lib/sys/xserial_write.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/com32/lib/sys/serial_write.c b/com32/lib/sys/serial_write.c
index 0235620..b593083 100644
--- a/com32/lib/sys/serial_write.c
+++ b/com32/lib/sys/serial_write.c
@@ -35,6 +35,7 @@
 #include <string.h>
 #include <com32.h>
 #include <minmax.h>
+#include <syslinux/config.h>
 #include "file.h"
 
 ssize_t __serial_write(struct file_info *fp, const void *buf, size_t count)
@@ -45,6 +46,9 @@ ssize_t __serial_write(struct file_info *fp, const void *buf, size_t count)
 
   (void)fp;
 
+  if (!syslinux_serial_console_info()->iobase)
+    return count;		/* Nothing to do */
+
   memset(&ireg, 0, sizeof ireg);
   ireg.eax.b[1] = 0x04;
 
diff --git a/com32/lib/sys/xserial_write.c b/com32/lib/sys/xserial_write.c
index ebdf296..7964042 100644
--- a/com32/lib/sys/xserial_write.c
+++ b/com32/lib/sys/xserial_write.c
@@ -37,6 +37,7 @@
 #include <com32.h>
 #include <minmax.h>
 #include <colortbl.h>
+#include <syslinux/config.h>
 #include "file.h"
 
 static void emit(char ch)
@@ -61,6 +62,9 @@ ssize_t __xserial_write(struct file_info *fp, const void *buf, size_t count)
 
   (void)fp;
 
+  if (!syslinux_serial_console_info()->iobase)
+    return count;		/* Nothing to do */
+
   while ( count-- ) {
     unsigned char ch = *bufp++;
 
-- 
2.7.4