genirq: Introduce request_any_context_irq()

Now that we enjoy threaded interrupts, we're starting to see irq_chip
implementations (wm831x, pca953x) that make use of threaded interrupts
for the controller, and nested interrupts for the client interrupt. It
all works very well, with one drawback:

Drivers requesting an IRQ must now know whether the handler will
run in a thread context or not, and call request_threaded_irq() or
request_irq() accordingly.

The problem is that the requesting driver sometimes doesn't know
about the nature of the interrupt, specially when the interrupt
controller is a discrete chip (typically a GPIO expander connected
over I2C) that can be connected to a wide variety of otherwise perfectly
supported hardware.

This patch introduces the request_any_context_irq() function that mostly
mimics the usual request_irq(), except that it checks whether the irq
level is configured as nested or not, and calls the right backend.
On success, it also returns either IRQC_IS_HARDIRQ or IRQC_IS_NESTED.

[ tglx: Made return value an enum, simplified code and made the export
  	of request_any_context_irq GPL ]

Signed-off-by: Marc Zyngier <maz@misterjones.org>
Cc: <joachim.eastwood@jotron.com>
LKML-Reference: <927ea285bd0c68934ddae1a47e44a9ba@localhost>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 75f3f00ac1e5..d7e7a7660c6c 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -77,6 +77,18 @@ enum {
         IRQTF_AFFINITY,
 };
 
+/**
+ * These values can be returned by request_any_context_irq() and
+ * describe the context the interrupt will be run in.
+ *
+ * IRQC_IS_HARDIRQ - interrupt runs in hardirq context
+ * IRQC_IS_NESTED - interrupt runs in a nested threaded context
+ */
+enum {
+        IRQC_IS_HARDIRQ = 0,
+        IRQC_IS_NESTED,
+};
+
 typedef irqreturn_t (*irq_handler_t)(int, void *);
 
 /**
@@ -120,6 +132,10 @@ request_irq(unsigned int irq, irq_handler_t handler, unsigned long flags,
         return request_threaded_irq(irq, handler, NULL, flags, name, dev);
 }
 
+extern int __must_check
+request_any_context_irq(unsigned int irq, irq_handler_t handler,
+                        unsigned long flags, const char *name, void *dev_id);
+
 extern void exit_irq_thread(void);
 #else
 
@@ -141,6 +157,13 @@ request_threaded_irq(unsigned int irq, irq_handler_t handler,
         return request_irq(irq, handler, flags, name, dev);
 }
 
+static inline int __must_check
+request_any_context_irq(unsigned int irq, irq_handler_t handler,
+                        unsigned long flags, const char *name, void *dev_id)
+{
+        return request_irq(irq, handler, flags, name, dev_id);
+}
+
 static inline void exit_irq_thread(void) { }
 #endif