[PATCH] genirq: irq: add a dynamic irq creation API

With the msi support comes a new concept in irq handling, irqs that are
created dynamically at run time.

Currently the msi code allocates irqs backwards.  First it allocates a
platform dependent routing value for an interrupt the ``vector'' and then it
figures out from the vector which irq you are on.

This msi backwards allocator suffers from two basic problems.  The allocator
suffers because it is trying to do something that is architecture specific in
a generic way making it brittle, inflexible, and tied to tightly to the
architecture implementation.  The alloctor also suffers from it's very
backwards nature as it has tied things together that should have no
dependencies.

To solve the basic dynamic irq allocation problem two new architecture
specific functions are added: create_irq and destroy_irq.

create_irq takes no input and returns an unused irq number, that won't be
reused until it is returned to the free poll with destroy_irq.  The irq then
can be used for any purpose although the only initial consumer is the msi
code.

destroy_irq takes an irq number allocated with create_irq and returns it to
the free pool.

Making this functionality per architecture increases the simplicity of the irq
allocation code and increases it's flexibility.

dynamic_irq_init() and dynamic_irq_cleanup() are added to automate the
irq_desc initializtion that should happen for dynamic irqs.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rajesh Shah <rajesh.shah@intel.com>
Cc: Andi Kleen <ak@muc.de>
Cc: "Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 56 insertions, 0 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 736cb0b..0dc2438 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -18,6 +18,62 @@
 #include "internals.h"
 
 /**
+ *	dynamic_irq_init - initialize a dynamically allocated irq
+ *	@irq:	irq number to initialize
+ */
+void dynamic_irq_init(unsigned int irq)
+{
+	struct irq_desc *desc;
+	unsigned long flags;
+
+	if (irq >= NR_IRQS) {
+		printk(KERN_ERR "Trying to initialize invalid IRQ%d\n", irq);
+		WARN_ON(1);
+		return;
+	}
+
+	/* Ensure we don't have left over values from a previous use of this irq */
+	desc = irq_desc + irq;
+	spin_lock_irqsave(&desc->lock, flags);
+	desc->status = IRQ_DISABLED;
+	desc->chip = &no_irq_chip;
+	desc->handle_irq = handle_bad_irq;
+	desc->depth = 1;
+	desc->handler_data = NULL;
+	desc->chip_data = NULL;
+	desc->action = NULL;
+	desc->irq_count = 0;
+	desc->irqs_unhandled = 0;
+#ifdef CONFIG_SMP
+	desc->affinity = CPU_MASK_ALL;
+#endif
+	spin_unlock_irqrestore(&desc->lock, flags);
+}
+
+/**
+ *	dynamic_irq_cleanup - cleanup a dynamically allocated irq
+ *	@irq:	irq number to initialize
+ */
+void dynamic_irq_cleanup(unsigned int irq)
+{
+	struct irq_desc *desc;
+	unsigned long flags;
+
+	if (irq >= NR_IRQS) {
+		printk(KERN_ERR "Trying to cleanup invalid IRQ%d\n", irq);
+		WARN_ON(1);
+		return;
+	}
+
+	desc = irq_desc + irq;
+	spin_lock_irqsave(&desc->lock, flags);
+	desc->handle_irq = handle_bad_irq;
+	desc->chip = &no_irq_chip;
+	spin_unlock_irqrestore(&desc->lock, flags);
+}
+
+
+/**
  *	set_irq_chip - set the irq chip for an irq
  *	@irq:	irq number
  *	@chip:	pointer to irq chip description structure