feat(sdei): add a function to return total number of events registered

This patch adds a public API to return the total number of registered
events. The purpose of this is primarily for DRTM to ensure that no
SDEI event can interfere with a dynamic launch.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I1d1cba2da7d5566cc340620ee1ce7d7844740b86
diff --git a/include/services/sdei.h b/include/services/sdei.h
index 063ed6f..c12a182 100644
--- a/include/services/sdei.h
+++ b/include/services/sdei.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2022, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -137,4 +137,7 @@
 /* Public API to dispatch an event to Normal world */
 int sdei_dispatch_event(int ev_num);
 
+/* Public API to check how many SDEI events are registered. */
+int sdei_get_registered_event_count(void);
+
 #endif /* SDEI_H */
diff --git a/services/std_svc/sdei/sdei_event.c b/services/std_svc/sdei/sdei_event.c
index 0b608e1..e0c7971 100644
--- a/services/std_svc/sdei/sdei_event.c
+++ b/services/std_svc/sdei/sdei_event.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2022, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -99,3 +99,24 @@
 
 	return NULL;
 }
+
+/*
+ * Return the total number of currently registered SDEI events.
+ */
+int sdei_get_registered_event_count(void)
+{
+	const sdei_mapping_t *mapping;
+	sdei_ev_map_t *map;
+	unsigned int i;
+	unsigned int j;
+	int count = 0;
+
+	/* Add up reg counts for each mapping. */
+	for_each_mapping_type(i, mapping) {
+		iterate_mapping(mapping, j, map) {
+			count += map->reg_count;
+		}
+	}
+
+	return count;
+}