--- cups-1.2rc2/backend/serial.c	2006-03-07 23:07:44.000000000 +0100
+++ cups-1.2rc2.new/backend/serial.c	2006-04-13 15:44:03.000000000 +0200
@@ -87,6 +87,10 @@
 #  include <IOKit/IOBSD.h>
 #endif /* __APPLE__ */
 
+#if defined(__linux) || defined(linux) || defined(__linux__)
+#  include <linux/serial.h>
+#  include <linux/ioctl.h>
+#endif
 
 /*
  * Local functions...
@@ -670,13 +674,22 @@
   int	i, j;		/* Looping vars */
   int	fd;		/* File descriptor */
   char	device[255];	/* Device filename */
-
+  struct serial_struct serinfo; /* serial port info */
 
   for (i = 0; i < 100; i ++)
   {
     sprintf(device, "/dev/ttyS%d", i);
     if ((fd = open(device, O_WRONLY | O_NOCTTY | O_NDELAY)) >= 0)
     {
+      serinfo.reserved_char[0] = 0; /* setserial does this as well */
+      if (ioctl(fd, TIOCGSERIAL, &serinfo)!=-1) /* unsupported ioctl? */
+      {
+	if (serinfo.type==PORT_UNKNOWN)
+	{
+	  close(fd);
+	  continue;
+	}
+      }
       close(fd);
 #  if defined(_ARCH_PPC) || defined(powerpc) || defined(__powerpc)
       printf("serial serial:%s?baud=230400 \"Unknown\" \"Serial Port #%d\"\n",