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>

3 files changed, 2 insertions, 5 deletions

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 728cc30d04ea..fe0b09dceb7d 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -36,9 +36,6 @@ extern atomic_t ppc_n_lost_interrupts;
 /* Total number of virq in the platform */
 #define NR_IRQS         CONFIG_NR_IRQS
 
-/* Number of irqs reserved for the legacy controller */
-#define NUM_ISA_INTERRUPTS      16
-
 /* Same thing, used by the generic IRQ code */
 #define NR_IRQS_LEGACY          NUM_ISA_INTERRUPTS
 
diff --git a/arch/powerpc/sysdev/i8259.c b/arch/powerpc/sysdev/i8259.c
index 573a73bd954a..997df6a7ab5d 100644
--- a/arch/powerpc/sysdev/i8259.c
+++ b/arch/powerpc/sysdev/i8259.c
@@ -263,7 +263,7 @@ void i8259_init(struct device_node *node, unsigned long intack_addr)
         raw_spin_unlock_irqrestore(&i8259_lock, flags);
 
         /* create a legacy host */
-        i8259_host = irq_domain_add_legacy(node, &i8259_host_ops, NULL);
+        i8259_host = irq_domain_add_legacy_isa(node, &i8259_host_ops, NULL);
         if (i8259_host == NULL) {
                 printk(KERN_ERR "i8259: failed to allocate irq host !\n");
                 return;
diff --git a/arch/powerpc/sysdev/tsi108_pci.c b/arch/powerpc/sysdev/tsi108_pci.c
index 1be26f4b9c96..188012c58f7f 100644
--- a/arch/powerpc/sysdev/tsi108_pci.c
+++ b/arch/powerpc/sysdev/tsi108_pci.c
@@ -419,7 +419,7 @@ void __init tsi108_pci_int_init(struct device_node *node)
 {
         DBG("Tsi108_pci_int_init: initializing PCI interrupts\n");
 
-        pci_irq_host = irq_domain_add_legacy(node, &pci_irq_domain_ops, NULL);
+        pci_irq_host = irq_domain_add_legacy_isa(node, &pci_irq_domain_ops, NULL);
         if (pci_irq_host == NULL) {
                 printk(KERN_ERR "pci_irq_host: failed to allocate irq domain!\n");
                 return;