+/*
+ * ISA irqs by default are the first 16 gsis but can be
+ * any gsi as specified by an interrupt source override.
+ */
+static u32 isa_irq_to_gsi[NR_IRQS_LEGACY] __read_mostly = {
+ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+};
+
+static unsigned int gsi_to_irq(unsigned int gsi)
+{
+ unsigned int irq = gsi + NR_IRQS_LEGACY;
+ unsigned int i;
+
+ for (i = 0; i < NR_IRQS_LEGACY; i++) {
+ if (isa_irq_to_gsi[i] == gsi) {
+ return i;
+ }
+ }
+
+ /* Provide an identity mapping of gsi == irq
+ * except on truly weird platforms that have
+ * non isa irqs in the first 16 gsis.
+ */
+ if (gsi >= NR_IRQS_LEGACY)
+ irq = gsi;
+ else
+ irq = gsi_end + 1 + gsi;
+
+ return irq;
+}
+
+static u32 irq_to_gsi(int irq)
+{
+ unsigned int gsi;
+
+ if (irq < NR_IRQS_LEGACY)
+ gsi = isa_irq_to_gsi[irq];
+ else if (irq <= gsi_end)
+ gsi = irq;
+ else if (irq <= (gsi_end + NR_IRQS_LEGACY))
+ gsi = irq - gsi_end;
+ else
+ gsi = 0xffffffff;
+
+ return gsi;
+}
+