xen/evtchn: support more than 4096 ports

Remove the check during unbind for NR_EVENT_CHANNELS as this limits
support to less than 4096 ports.

Signed-off-by: David Vrabel <[e-mail]>
Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>

drivers/xen/events/events_base.c

···
 	return rc;
 }
 
+/**
+ * xen_evtchn_nr_channels - number of usable event channel ports
+ *
+ * This may be less than the maximum supported by the current
+ * hypervisor ABI. Use xen_evtchn_max_channels() for the maximum
+ * supported.
+ */
+unsigned xen_evtchn_nr_channels(void)
+{
+        return evtchn_ops->nr_channels();
+}
+EXPORT_SYMBOL_GPL(xen_evtchn_nr_channels);
+
 int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 {
 	struct evtchn_bind_virq bind_virq;

drivers/xen/events/events_internal.h

···
 	return evtchn_ops->max_channels();
 }
 
-static inline unsigned xen_evtchn_nr_channels(void)
-{
-	return evtchn_ops->nr_channels();
-}
-
 /*
  * Do any ABI specific setup for a bound event channel before it can
  * be unmasked and used.

drivers/xen/evtchn.c

···
 			break;
 
 		rc = -EINVAL;
-		if (unbind.port >= NR_EVENT_CHANNELS)
+		if (unbind.port >= xen_evtchn_nr_channels())
 			break;
 
 		rc = -ENOTCONN;

include/xen/events.h

···
 #include <asm/xen/hypercall.h>
 #include <asm/xen/events.h>
 
+unsigned xen_evtchn_nr_channels(void);
+
 int bind_evtchn_to_irq(unsigned int evtchn);
 int bind_evtchn_to_irqhandler(unsigned int evtchn,
 			      irq_handler_t handler,