irq_domain: Add support for base irq and hwirq in legacy mappings

Add support for a legacy mapping where irq = (hwirq - first_hwirq + first_irq)
so that a controller driver can allocate a fixed range of irq_descs and use
a simple calculation to translate back and forth between linux and hw irq
numbers.  This is needed to use an irq_domain with many of the ARM interrupt
controller drivers that manage their own irq_desc allocations.  Ultimately
the goal is to migrate those drivers to use the linear revmap, but doing it
this way allows each driver to be converted separately which makes the
migration path easier.

This patch generalizes the IRQ_DOMAIN_MAP_LEGACY method to use
(first_irq-first_hwirq) as the offset between hwirq and linux irq number,
and adds checks to make sure that the hwirq number does not exceed range
assigned to the controller.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Milton Miller <miltonm@bga.com>
Tested-by: Olof Johansson <olof@lixom.net>

1 files changed, 19 insertions, 1 deletions

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index f95553f..7fef39e 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -39,6 +39,9 @@ struct device_node;
 struct irq_domain;
 struct of_device_id;
 
+/* Number of irqs reserved for a legacy isa controller */
+#define NUM_ISA_INTERRUPTS	16
+
 /* This type is the placeholder for a hardware interrupt number. It has to
  * be big enough to enclose whatever representation is used by a given
  * platform.
@@ -98,6 +101,11 @@ struct irq_domain {
 	union {
 		struct {
 			unsigned int size;
+			unsigned int first_irq;
+			irq_hw_number_t first_hwirq;
+		} legacy;
+		struct {
+			unsigned int size;
 			unsigned int *revmap;
 		} linear;
 		struct radix_tree_root tree;
@@ -117,6 +125,9 @@ struct irq_domain {
 #ifdef CONFIG_IRQ_DOMAIN
 #ifdef CONFIG_PPC
 struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
+					 unsigned int size,
+					 unsigned int first_irq,
+					 irq_hw_number_t first_hwirq,
 					 struct irq_domain_ops *ops,
 					 void *host_data);
 struct irq_domain *irq_domain_add_linear(struct device_node *of_node,
@@ -130,11 +141,18 @@ struct irq_domain *irq_domain_add_tree(struct device_node *of_node,
 					 struct irq_domain_ops *ops,
 					 void *host_data);
 
-
 extern struct irq_domain *irq_find_host(struct device_node *node);
 extern void irq_set_default_host(struct irq_domain *host);
 extern void irq_set_virq_count(unsigned int count);
 
+static inline struct irq_domain *irq_domain_add_legacy_isa(
+				struct device_node *of_node,
+				struct irq_domain_ops *ops,
+				void *host_data)
+{
+	return irq_domain_add_legacy(of_node, NUM_ISA_INTERRUPTS, 0, 0, ops,
+				     host_data);
+}
 
 extern unsigned int irq_create_mapping(struct irq_domain *host,
 				       irq_hw_number_t hwirq);