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.

2 files changed, 8 insertions, 0 deletions

diff --git a/com32/lib/sys/serial_write.c b/com32/lib/sys/serial_write.c
index 0235620b..b5930833 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 ebdf296b..7964042e 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++;