libxc: NetBSD: implement xc_evtchn_bind_unbound_port.

Doesn't actually appear to be used anywhere but is defined for other
OSes.

The NetBSD evtchn.h contains comments "Return allocated port" for
several ioctls which currently return the allocated port as a member
of the argument structure and not as the ioctl return value (I think
this is a cut and paste error).

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Christoph Egger <Christoph.Egger@amd.com>
committer: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/include/xen-sys/NetBSD/evtchn.h

@@ -33,7 +33,6 @@
 
 /*
  * Bind a fresh port to VIRQ @virq.
- * Return allocated port.
  */
 #define IOCTL_EVTCHN_BIND_VIRQ				\
 	_IOWR('E', 4, struct ioctl_evtchn_bind_virq)
@@ -44,7 +43,6 @@ struct ioctl_evtchn_bind_virq {
 
 /*
  * Bind a fresh port to remote <@remote_domain, @remote_port>.
- * Return allocated port.
  */
 #define IOCTL_EVTCHN_BIND_INTERDOMAIN			\
 	_IOWR('E', 5, struct ioctl_evtchn_bind_interdomain)
@@ -55,7 +53,6 @@ struct ioctl_evtchn_bind_interdomain {
 
 /*
  * Allocate a fresh port for binding to @remote_domain.
- * Return allocated port.
  */
 #define IOCTL_EVTCHN_BIND_UNBOUND_PORT			\
 	_IOWR('E', 6, struct ioctl_evtchn_bind_unbound_port)

tools/libxc/xc_netbsd.c

@@ -205,6 +205,21 @@ int xc_evtchn_notify(int xce_handle, evtchn_port_t port)
     return ioctl(xce_handle, IOCTL_EVTCHN_NOTIFY, &notify);
 }
 
+evtchn_port_or_error_t
+xc_evtchn_bind_unbound_port(int xce_handle, int domid)
+{
+    struct ioctl_evtchn_bind_unbound_port bind;
+    int ret;
+
+    bind.remote_domain = domid;
+
+    ret = ioctl(xce_handle, IOCTL_EVTCHN_BIND_UNBOUND_PORT, &bind);
+    if (ret == 0)
+	return bind.port;
+    else
+	return -1;
+}
+
 evtchn_port_or_error_t
 xc_evtchn_bind_interdomain(int xce_handle, int domid,
                            evtchn_port_t remote_port)