--- linux-2.6.21.5.orig/drivers/serial/8250_pci.c	2007-04-26 06:08:32.000000000 +0300
+++ linux-2.6.21.5/drivers/serial/8250_pci.c	2007-07-05 17:26:32.000000000 +0300
@@ -1513,6 +1513,11 @@
 	},
 };
 
+static const struct pci_device_id softmodem_blacklist[] = {
+     { PCI_VDEVICE ( AL, 0x5457 ), }, /* ALi Corporation M5457 AC'97 Modem */
+     { }
+};
+
 /*
  * Given a complete unknown PCI device, try to use some heuristics to
  * guess what the configuration might be, based on the pitiful PCI
@@ -1521,6 +1526,7 @@
 static int __devinit
 serial_pci_guess_board(struct pci_dev *dev, struct pciserial_board *board)
 {
+        const struct pci_device_id * blacklist;
 	int num_iomem, num_port, first_port = -1, i;
 	
 	/*
@@ -1535,6 +1541,16 @@
 	    (dev->class & 0xff) > 6)
 		return -ENODEV;
 
+	/*
+	 * Do not access blacklisted devices that are known not to
+	 * feature serial ports.
+	 */
+	for (blacklist = softmodem_blacklist; blacklist->vendor; blacklist++) {
+	        if ((dev->vendor == blacklist->vendor) &&
+	            (dev->device == blacklist->device))
+		        return -ENODEV;
+	}
+	
 	num_iomem = num_port = 0;
 	for (i = 0; i < PCI_NUM_BAR_RESOURCES; i++) {
 		if (pci_resource_flags(dev, i) & IORESOURCE_IO) {