+/*
+ * Handle the $IRT PCI IRQ Routing Table format used by AMI for its BCP
+ * (BIOS Configuration Program) external tool meant for tweaking BIOS
+ * structures without the need to rebuild it from sources. The $IRT
+ * format has been invented by AMI before Microsoft has come up with its
+ * $PIR format and a $IRT table is therefore there in some systems that
+ * lack a $PIR table.
+ *
+ * It uses the same PCI BIOS 2.1 format for interrupt routing entries
+ * themselves but has a different simpler header prepended instead,
+ * occupying 8 bytes, where a `$IRT' signature is followed by one byte
+ * specifying the total number of interrupt routing entries allocated in
+ * the table, then one byte specifying the actual number of entries used
+ * (which the BCP tool can take advantage of when modifying the table),
+ * and finally a 16-bit word giving the IRQs devoted exclusively to PCI.
+ * Unlike with the $PIR table there is no alignment guarantee.
+ *
+ * Given the similarity of the two formats the $IRT one is trivial to
+ * convert to the $PIR one, which we do here, except that obviously we
+ * have no information as to the router device to use, but we can handle
+ * it by matching PCI device IDs actually seen on the bus against ones
+ * that our individual routers recognise.
+ *
+ * Reportedly there is another $IRT table format where a 16-bit word
+ * follows the header instead that points to interrupt routing entries
+ * in a $PIR table provided elsewhere. In that case this code will not
+ * be reached though as the $PIR table will have been chosen instead.
+ */
+static inline struct irq_routing_table *pirq_convert_irt_table(u8 *addr,
+ u8 *limit)
+{
+ struct irt_routing_table *ir;
+ struct irq_routing_table *rt;
+ u16 size;
+ u8 sum;
+ int i;
+
+ ir = (struct irt_routing_table *)addr;
+ if (ir->signature != IRT_SIGNATURE || !ir->used || ir->size < ir->used)
+ return NULL;
+
+ size = sizeof(*ir) + ir->used * sizeof(ir->slots[0]);
+ if (size > limit - addr)
+ return NULL;
+
+ DBG(KERN_DEBUG "PCI: $IRT Interrupt Routing Table found at 0x%lx\n",
+ __pa(ir));
+
+ size = sizeof(*rt) + ir->used * sizeof(rt->slots[0]);
+ rt = kzalloc(size, GFP_KERNEL);
+ if (!rt)
+ return NULL;