xen: Port Xen event channel driver from mini-os

Make required updates to run on u-boot. Strip functionality
not needed by U-boot.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>

include/xen/events.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * (C) 2003 - Rolf Neugebauer - Intel Research Cambridge
+ * (C) 2005 - Grzegorz Milos - Intel Reseach Cambridge
+ * (C) 2020 - EPAM Systems Inc.
+ *
+ * File: events.h
+ * Author: Rolf Neugebauer (neugebar@dcs.gla.ac.uk)
+ * Changes: Grzegorz Milos (gm281@cam.ac.uk)
+ *
+ * Date: Jul 2003, changes Jun 2005
+ *
+ * Description: Deals with events on the event channels
+ */
+#ifndef _EVENTS_H_
+#define _EVENTS_H_
+
+#include <asm/xen/hypercall.h>
+#include <xen/interface/event_channel.h>
+
+void init_events(void);
+void fini_events(void);
+
+int do_event(evtchn_port_t port, struct pt_regs *regs);
+void unbind_evtchn(evtchn_port_t port);
+void unbind_all_ports(void);
+int evtchn_alloc_unbound(domid_t pal,
+			 void (*handler)(evtchn_port_t, struct pt_regs *, void *),
+			 void *data, evtchn_port_t *port);
+
+/* Send notification via event channel */
+static inline int notify_remote_via_evtchn(evtchn_port_t port)
+{
+	struct evtchn_send op;
+
+	op.port = port;
+	return HYPERVISOR_event_channel_op(EVTCHNOP_send, &op);
+}
+
+void eventchn_poll(void);
+
+#endif /* _EVENTS_H_ */