feat(fconf): add a helper to get image index

A new function dyn_cfg_dtb_info_get_index() is created to get the index
of the given image config_id in the dtb_infos pool.
This allows checking if an image with a specific ID is in the FIP.

Change-Id: Ib300ed08e5b8a683dc7980a90221c305fb3f457d
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/include/lib/fconf/fconf_dyn_cfg_getter.h b/include/lib/fconf/fconf_dyn_cfg_getter.h
index 6f8da0d..ff51c6c 100644
--- a/include/lib/fconf/fconf_dyn_cfg_getter.h
+++ b/include/lib/fconf/fconf_dyn_cfg_getter.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2019-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,6 +9,8 @@
 
 #include <lib/fconf/fconf.h>
 
+#define FCONF_INVALID_IDX	0xFFFFFFFFU
+
 /* Dynamic configuration related getter */
 #define dyn_cfg__dtb_getter(id)	dyn_cfg_dtb_info_getter(id)
 
@@ -18,6 +20,7 @@
 	unsigned int config_id;
 };
 
+unsigned int dyn_cfg_dtb_info_get_index(unsigned int config_id);
 struct dyn_cfg_dtb_info_t *dyn_cfg_dtb_info_getter(unsigned int config_id);
 int fconf_populate_dtb_registry(uintptr_t config);
 
diff --git a/lib/fconf/fconf_dyn_cfg_getter.c b/lib/fconf/fconf_dyn_cfg_getter.c
index 25dd7f9..34623fb 100644
--- a/lib/fconf/fconf_dyn_cfg_getter.c
+++ b/lib/fconf/fconf_dyn_cfg_getter.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2019-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -40,17 +40,30 @@
 	dtb_info->config_id = config_id;
 }
 
-struct dyn_cfg_dtb_info_t *dyn_cfg_dtb_info_getter(unsigned int config_id)
+/* Get index of the config_id image */
+unsigned int dyn_cfg_dtb_info_get_index(unsigned int config_id)
 {
 	unsigned int index;
 
 	/* Positions index to the proper config-id */
 	for (index = 0U; index < MAX_DTB_INFO; index++) {
 		if (dtb_infos[index].config_id == config_id) {
-			return &dtb_infos[index];
+			return index;
 		}
 	}
 
+	return FCONF_INVALID_IDX;
+}
+
+struct dyn_cfg_dtb_info_t *dyn_cfg_dtb_info_getter(unsigned int config_id)
+{
+	/* Positions index to the proper config-id */
+	unsigned int index = dyn_cfg_dtb_info_get_index(config_id);
+
+	if (index < MAX_DTB_INFO) {
+		return &dtb_infos[index];
+	}
+
 	WARN("FCONF: Invalid config id %u\n", config_id);
 
 	return NULL;