Index: runloop.c
===================================================================
--- runloop.c	(revision 5719)
+++ runloop.c	(working copy)
@@ -53,6 +53,7 @@
 		total_bytes,		/* Total bytes written */
 		bytes;			/* Bytes written */
   int		paperout;		/* "Paper out" status */
+  int		offline;		/* "Off-line" status */
   char		print_buffer[8192],	/* Print data buffer */
 		*print_ptr,		/* Pointer into print data buffer */
 		bc_buffer[1024];	/* Back-channel data buffer */
@@ -61,6 +62,9 @@
 #endif /* HAVE_SIGACTION && !HAVE_SIGSET */
 
 
+  fprintf(stderr, "DEBUG: backendRunLoop(print_fd=%d, device_fd=%d, use_bc=%d)\n",
+          print_fd, device_fd, use_bc);
+
  /*
   * If we are printing data from a print driver on stdin, ignore SIGTERM
   * so that the driver can finish out any page data, e.g. to eject the
@@ -93,7 +97,7 @@
   * Now loop until we are out of data from print_fd...
   */
 
-  for (print_bytes = 0, print_ptr = print_buffer, paperout = 0, total_bytes = 0;;)
+  for (print_bytes = 0, print_ptr = print_buffer, offline = 0, paperout = 0, total_bytes = 0;;)
   {
    /*
     * Use select() to determine whether we have data to copy around...
@@ -106,12 +110,36 @@
       FD_SET(device_fd, &input);
 
     FD_ZERO(&output);
-    if (print_bytes)
+    if (print_bytes || !use_bc)
       FD_SET(device_fd, &output);
 
-    if (select(nfds, &input, &output, NULL, NULL) < 0)
-      continue;				/* Ignore errors here */
+    if (use_bc)
+    {
+      if (select(nfds, &input, &output, NULL, NULL) < 0)
+      {
+       /*
+	* Pause printing to clear any pending errors...
+	*/
 
+	if (errno == ENXIO && !offline)
+	{
+	  fputs("STATE: +offline-error\n", stderr);
+	  fputs("INFO: Printer is currently off-line.\n", stderr);
+	  offline = 1;
+	}
+
+	sleep(1);
+	continue;
+      }
+
+      if (offline)
+      {
+	fputs("STATE: -offline-error\n", stderr);
+	fputs("INFO: Printer is now on-line.\n", stderr);
+	offline = 0;
+      }
+    }
+
    /*
     * Check if we have back-channel data ready...
     */
@@ -158,6 +186,9 @@
       }
 
       print_ptr = print_buffer;
+
+      fprintf(stderr, "DEBUG: Read %d bytes of print data...\n",
+              (int)print_bytes);
     }
 
    /*
@@ -196,7 +227,7 @@
 	  paperout = 0;
 	}
 
-        fprintf(stderr, "DEBUG: Wrote %d bytes...\n", (int)bytes);
+        fprintf(stderr, "DEBUG: Wrote %d bytes of print data...\n", (int)bytes);
 
         print_bytes -= bytes;
 	print_ptr   += bytes;
Index: usb-unix.c
===================================================================
--- usb-unix.c	(revision 5719)
+++ usb-unix.c	(working copy)
@@ -44,7 +44,7 @@
  * Local functions...
  */
 
-int	open_device(const char *uri);
+int	open_device(const char *uri, int *use_bc);
 
 
 /*
@@ -75,14 +75,6 @@
   (void)argv;
 
  /*
-  * Disable backchannel data when printing to Canon USB printers - apparently
-  * Canon printers will return the IEEE-1284 device ID over and over and over
-  * when they get a read request...
-  */
-
-  use_bc = strcasecmp(hostname, "Canon") != 0;
-
- /*
   * Open the USB port device...
   */
 
@@ -90,7 +82,15 @@
 
   do
   {
-    if ((device_fd = open_device(uri)) == -1)
+   /*
+    * Disable backchannel data when printing to Canon USB printers - apparently
+    * Canon printers will return the IEEE-1284 device ID over and over and over
+    * when they get a read request...
+    */
+
+    use_bc = strcasecmp(hostname, "Canon") != 0;
+
+    if ((device_fd = open_device(uri, &use_bc)) == -1)
     {
       if (getenv("CLASS") != NULL)
       {
@@ -195,7 +195,7 @@
       lseek(print_fd, 0, SEEK_SET);
     }
 
-    tbytes = backendRunLoop(print_fd, device_fd, 1);
+    tbytes = backendRunLoop(print_fd, device_fd, use_bc);
 
     if (print_fd != 0 && tbytes >= 0)
       fprintf(stderr, "INFO: Sent print file, " CUPS_LLFMT " bytes...\n",
@@ -277,7 +277,7 @@
   {
     sprintf(device, "/dev/usb/printer%d", i);
 
-    if ((fd = open(device, O_RDWR | O_EXCL)) >= 0)
+    if ((fd = open(device, O_WRONLY | O_EXCL)) >= 0)
     {
       if (!backendGetDeviceID(fd, device_id, sizeof(device_id),
                               make_model, sizeof(make_model),
@@ -314,8 +314,12 @@
  */
 
 int					/* O - File descriptor or -1 on error */
-open_device(const char *uri)		/* I - Device URI */
+open_device(const char *uri,		/* I - Device URI */
+            int        *use_bc)		/* O - Set to 0 for unidirectional */
 {
+  int	fd;				/* File descriptor */
+
+
  /*
   * The generic implementation just treats the URI as a device filename...
   * Specific operating systems may also support using the device serial
@@ -340,7 +344,6 @@
 
     int		i;			/* Looping var */
     int		busy;			/* Are any ports busy? */
-    int		fd;			/* File descriptor */
     char	format[255],		/* Format for device filename */
 		device[255],		/* Device filename */
 		device_id[1024],	/* Device ID string */
@@ -446,7 +449,6 @@
 
     int		i;			/* Looping var */
     int		busy;			/* Are any ports busy? */
-    int		fd;			/* File descriptor */
     char	device[255],		/* Device filename */
 		device_id[1024],	/* Device ID string */
 		make_model[1024],	/* Make and model */
@@ -463,7 +465,7 @@
       {
 	sprintf(device, "/dev/usb/printer%d", i);
 
-	if ((fd = open(device, O_RDWR | O_EXCL)) >= 0)
+	if ((fd = open(device, O_WRONLY | O_EXCL)) >= 0)
 	  backendGetDeviceID(fd, device_id, sizeof(device_id),
                              make_model, sizeof(make_model),
 			     "usb", device_uri, sizeof(device_uri));
@@ -481,8 +483,18 @@
         }
 
         if (!strcmp(uri, device_uri))
-	  return (fd);	/* Yes, return this file descriptor... */
+	{
+	 /*
+	  * Yes, return this file descriptor...
+	  */
 
+          fputs("DEBUG: Setting use_bc to 0!\n", stderr);
+
+          *use_bc = 0;
+
+	  return (fd);
+	}
+
        /*
 	* This wasn't the one...
 	*/
@@ -514,7 +526,15 @@
     return (-1);
   }
 #else
-    return (open(uri + 4, O_RDWR | O_EXCL));
+  {
+    if ((fd = open(uri + 4, O_RDWR | O_EXCL)) < 0)
+    {
+      fd      = open(uri + 4, O_WRONLY | O_EXCL);
+      *use_bc = 0;
+    }
+
+    return (fd);
+  }
 #endif /* __linux */
   else
   {