diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index 848bb97..364f4b7 100644
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -457,7 +457,11 @@
 	return 0;
 }
 
-unsigned int acpi_register_gsi(u32 gsi, int edge_level, int active_high_low)
+/*
+ * success: return IRQ number (>=0)
+ * failure: return < 0
+ */
+int acpi_register_gsi(u32 gsi, int edge_level, int active_high_low)
 {
 	unsigned int irq;
 	unsigned int plat_gsi = gsi;
diff --git a/arch/ia64/kernel/acpi.c b/arch/ia64/kernel/acpi.c
index 1c118b7..7513ff9 100644
--- a/arch/ia64/kernel/acpi.c
+++ b/arch/ia64/kernel/acpi.c
@@ -565,7 +565,11 @@
 }
 #endif /* CONFIG_ACPI_NUMA */
 
-unsigned int
+/*
+ * success: return IRQ number (>=0)
+ * failure: return < 0
+ */
+int
 acpi_register_gsi (u32 gsi, int edge_level, int active_high_low)
 {
 	if (has_8259 && gsi < 16)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index ca0cd24..9378bcd 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -432,7 +432,7 @@
 
 #endif 	/*!CONFIG_ACPI_BOOT*/
 
-unsigned int acpi_register_gsi (u32 gsi, int edge_level, int active_high_low);
+int acpi_register_gsi (u32 gsi, int edge_level, int active_high_low);
 int acpi_gsi_to_irq (u32 gsi, unsigned int *irq);
 
 /*