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>

2 files changed, 60 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
 
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 704e488730a5..84f32278ff1f 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1120,3 +1120,40 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
         return retval;
 }
 EXPORT_SYMBOL(request_threaded_irq);
+
+/**
+ *      request_any_context_irq - allocate an interrupt line
+ *      @irq: Interrupt line to allocate
+ *      @handler: Function to be called when the IRQ occurs.
+ *                Threaded handler for threaded interrupts.
+ *      @flags: Interrupt type flags
+ *      @name: An ascii name for the claiming device
+ *      @dev_id: A cookie passed back to the handler function
+ *
+ *      This call allocates interrupt resources and enables the
+ *      interrupt line and IRQ handling. It selects either a
+ *      hardirq or threaded handling method depending on the
+ *      context.
+ *
+ *      On failure, it returns a negative value. On success,
+ *      it returns either IRQC_IS_HARDIRQ or IRQC_IS_NESTED.
+ */
+int request_any_context_irq(unsigned int irq, irq_handler_t handler,
+                            unsigned long flags, const char *name, void *dev_id)
+{
+        struct irq_desc *desc = irq_to_desc(irq);
+        int ret;
+
+        if (!desc)
+                return -EINVAL;
+
+        if (desc->status & IRQ_NESTED_THREAD) {
+                ret = request_threaded_irq(irq, NULL, handler,
+                                           flags, name, dev_id);
+                return !ret ? IRQC_IS_NESTED : ret;
+        }
+
+        ret = request_irq(irq, handler, flags, name, dev_id);
+        return !ret ? IRQC_IS_HARDIRQ : ret;
+}
+EXPORT_SYMBOL_GPL(request_any_context_irq);