fconf: initial commit

Introduce the Firmware CONfiguration Framework (fconf).

The fconf is an abstraction layer for platform specific data, allowing
a "property" to be queried and a value retrieved without the requesting
entity knowing what backing store is being used to hold the data.

The default backing store used is C structure. If another backing store
has to be used, the platform integrator needs to provide a "populate()"
function to fill the corresponding C structure.
The "populate()" function must be registered to the fconf framework with
the "FCONF_REGISTER_POPULATOR()". This ensures that the function would
be called inside the "fconf_populate()" function.

A two level macro is used as getter:
- the first macro takes 3 parameters and converts it to a function
  call: FCONF_GET_PROPERTY(a,b,c) -> a__b_getter(c).
- the second level defines a__b_getter(c) to the matching C structure,
  variable, array, function, etc..

Ex: Get a Chain of trust property:
    1) FCONF_GET_PROPERY(tbbr, cot, BL2_id) -> tbbr__cot_getter(BL2_id)
    2) tbbr__cot_getter(BL2_id) -> cot_desc_ptr[BL2_id]

Change-Id: Id394001353ed295bc680c3f543af0cf8da549469
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/drivers/auth/auth_mod.c b/drivers/auth/auth_mod.c
index 3fb2d1a..91ee1be 100644
--- a/drivers/auth/auth_mod.c
+++ b/drivers/auth/auth_mod.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,6 +16,7 @@
 #include <drivers/auth/auth_mod.h>
 #include <drivers/auth/crypto_mod.h>
 #include <drivers/auth/img_parser_mod.h>
+#include <lib/fconf/fconf_tbbr_getter.h>
 #include <plat/common/platform.h>
 
 /* ASN.1 tags */
@@ -302,9 +303,8 @@
 	const auth_img_desc_t *img_desc = NULL;
 
 	assert(parent_id != NULL);
-
 	/* Get the image descriptor */
-	img_desc = cot_desc_ptr[img_id];
+	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);
 
 	/* Check if the image has no parent (ROT) */
 	if (img_desc->parent == NULL) {
@@ -353,7 +353,7 @@
 	int rc, i;
 
 	/* Get the image descriptor from the chain of trust */
-	img_desc = cot_desc_ptr[img_id];
+	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);
 
 	/* Ask the parser to check the image integrity */
 	rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len);