xen/events: add a evtchn_op for port setup

Add a hook for port-specific setup and call it from
xen_irq_info_common_setup().

The FIFO-based ABIs may need to perform additional setup (expanding
the event array) before a bound event channel can start to receive
events.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/events/events_base.c

@@ -117,7 +117,7 @@ static int xen_irq_info_common_setup(struct irq_info *info,
 
 	irq_clear_status_flags(irq, IRQ_NOREQUEST|IRQ_NOAUTOEN);
 
-	return 0;
+	return xen_evtchn_port_setup(info);
 }
 
 static int xen_irq_info_evtchn_setup(unsigned irq,

drivers/xen/events/events_internal.h

@@ -55,6 +55,7 @@ struct irq_info {
 #define PIRQ_SHAREABLE	(1 << 1)
 
 struct evtchn_ops {
+	int (*setup)(struct irq_info *info);
 	void (*bind_to_cpu)(struct irq_info *info, unsigned cpu);
 
 	void (*clear_pending)(unsigned port);
@@ -75,6 +76,17 @@ struct irq_info *info_for_irq(unsigned irq);
 unsigned cpu_from_irq(unsigned irq);
 unsigned cpu_from_evtchn(unsigned int evtchn);
 
+/*
+ * Do any ABI specific setup for a bound event channel before it can
+ * be unmasked and used.
+ */
+static inline int xen_evtchn_port_setup(struct irq_info *info)
+{
+	if (evtchn_ops->setup)
+		return evtchn_ops->setup(info);
+	return 0;
+}
+
 static inline void xen_evtchn_port_bind_to_cpu(struct irq_info *info,
 					       unsigned cpu)
 {