ACPI : Not register gsi for PCI IDE controller in legacy mode

When PCI IDE controller works in legacy mode and no PRT entry is found
in ACPI PRT table, OSPM will neither read the irq number from the IDE
PCI configuration space nor call the function of acpi_register_gsi to
register gsi.

http://bugzilla.kernel.org/show_bug.cgi?id=5637

Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/pci_irq.c

@@ -429,6 +429,15 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
 					  &polarity, &link,
 					  acpi_pci_allocate_irq);
 
+	if (irq < 0) {
+		/*
+		 * IDE legacy mode controller IRQs are magic. Why do compat
+		 * extensions always make such a nasty mess.
+		 */
+		if (dev->class >> 8 == PCI_CLASS_STORAGE_IDE &&
+				(dev->class & 0x05) == 0)
+			return 0;
+	}
 	/*
 	 * No IRQ known to the ACPI subsystem - maybe the BIOS / 
 	 * driver reported one, then use it. Exit in any case.