[PATCH] x86: avoid wasting IRQs patch update

The patch addresses a problem with ACPI SCI interrupt entry, which gets
re-used, and the IRQ is assigned to another unrelated device.  The patch
corrects the code such that SCI IRQ is skipped and duplicate entry is
avoided.  Second issue came up with VIA chipset, the problem was caused by
original patch assigning IRQs starting 16 and up.  The VIA chipset uses
4-bit IRQ register for internal interrupt routing, and therefore cannot
handle IRQ numbers assigned to its devices.  The patch corrects this
problem by allowing PCI IRQs below 16.

Signed-off by: Natalie Protasevich <Natalie.Protasevich@unisys.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/mpparse.c

@@ -1116,7 +1116,15 @@ int mp_register_gsi (u32 gsi, int edge_level, int active_high_low)
 		 */
 		int irq = gsi;
 		if (gsi < MAX_GSI_NUM) {
-			gsi = pci_irq++;
+			if (gsi > 15)
+				gsi = pci_irq++;
+#ifdef CONFIG_ACPI_BUS
+			/*
+			 * Don't assign IRQ used by ACPI SCI
+			 */
+			if (gsi == acpi_fadt.sci_int)
+				gsi = pci_irq++;
+#endif
 			gsi_to_irq[irq] = gsi;
 		} else {
 			printk(KERN_ERR "GSI %u is too high\n", gsi);