acpi: use indirect call to register gsi in different modes

Rather than using a tree of conditionals, use function pointer
for acpi_register_gsi.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>

arch/x86/kernel/acpi/boot.c

@@ -513,35 +513,61 @@ int acpi_isa_irq_to_gsi(unsigned isa_irq, u32 *gsi)
 	return 0;
 }
 
-/*
- * success: return IRQ number (>=0)
- * failure: return < 0
- */
-int acpi_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
+static int acpi_register_gsi_pic(struct device *dev, u32 gsi,
+				 int trigger, int polarity)
 {
-	unsigned int irq;
-	unsigned int plat_gsi = gsi;
-
 #ifdef CONFIG_PCI
 	/*
 	 * Make sure all (legacy) PCI IRQs are set as level-triggered.
 	 */
-	if (acpi_irq_model == ACPI_IRQ_MODEL_PIC) {
-		if (trigger == ACPI_LEVEL_SENSITIVE)
-			eisa_set_level_irq(gsi);
-	}
+	if (trigger == ACPI_LEVEL_SENSITIVE)
+		eisa_set_level_irq(gsi);
 #endif
 
+	return gsi;
+}
+
+static int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
+				    int trigger, int polarity)
+{
 #ifdef CONFIG_X86_IO_APIC
-	if (acpi_irq_model == ACPI_IRQ_MODEL_IOAPIC) {
-		plat_gsi = mp_register_gsi(dev, gsi, trigger, polarity);
-	}
+	gsi = mp_register_gsi(dev, gsi, trigger, polarity);
 #endif
+
+	return gsi;
+}
+
+static int (*__acpi_register_gsi)(struct device *dev, u32 gsi, int trigger, int polarity) = acpi_register_gsi_pic;
+
+/*
+ * success: return IRQ number (>=0)
+ * failure: return < 0
+ */
+int acpi_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
+{
+	unsigned int irq;
+	unsigned int plat_gsi = gsi;
+
+	plat_gsi = (*__acpi_register_gsi)(dev, gsi, trigger, polarity);
 	irq = gsi_to_irq(plat_gsi);
 
 	return irq;
 }
 
+void __init acpi_set_irq_model_pic(void)
+{
+	acpi_irq_model = ACPI_IRQ_MODEL_PIC;
+	__acpi_register_gsi = acpi_register_gsi_pic;
+	acpi_ioapic = 0;
+}
+
+void __init acpi_set_irq_model_ioapic(void)
+{
+	acpi_irq_model = ACPI_IRQ_MODEL_IOAPIC;
+	__acpi_register_gsi = acpi_register_gsi_ioapic;
+	acpi_ioapic = 1;
+}
+
 /*
  *  ACPI based hotplug support for CPU
  */
@@ -1259,8 +1285,7 @@ static void __init acpi_process_madt(void)
 			 */
 			error = acpi_parse_madt_ioapic_entries();
 			if (!error) {
-				acpi_irq_model = ACPI_IRQ_MODEL_IOAPIC;
-				acpi_ioapic = 1;
+				acpi_set_irq_model_ioapic();
 
 				smp_found_config = 1;
 			}