diff --git a/src/compiler.h b/src/compiler.h
index 91b6e24..18e1a32 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -2,6 +2,8 @@
 #ifndef PLDM_COMPILER_H
 #define PLDM_COMPILER_H
 
+#include <libpldm/compiler.h>
+
 #ifndef __has_attribute
 #error The libpldm implementation requires __has_attribute
 #endif
@@ -20,8 +22,14 @@
 	int compliance;
 } pldm_required_attributes __attribute__((unused));
 
-#define LIBPLDM_CC_ALWAYS_INLINE      __attribute__((always_inline)) static inline
-#define LIBPLDM_CC_NONNULL	      __attribute__((nonnull))
+#ifndef LIBPLDM_CC_ALWAYS_INLINE
+#error Missing definition for LIBPLDM_ALWAYS_INLINE
+#endif
+
+#ifndef LIBPLDM_CC_NONNULL
+#error Missing definition for LIBPLDM_CC_NONNULL
+#endif
+
 #define LIBPLDM_CC_NONNULL_ARGS(...)  __attribute__((nonnull(__VA_ARGS__)))
 #define LIBPLDM_CC_UNUSED	      __attribute__((unused))
 #define LIBPLDM_CC_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
diff --git a/src/dsp/firmware_update.c b/src/dsp/firmware_update.c
index 2afcaab..d570d5c 100644
--- a/src/dsp/firmware_update.c
+++ b/src/dsp/firmware_update.c
@@ -473,6 +473,40 @@
 	return PLDM_SUCCESS;
 }
 
+LIBPLDM_ABI_TESTING
+int decode_pldm_descriptor_from_iter(struct pldm_descriptor_iter *iter,
+				     struct pldm_descriptor *desc)
+{
+	struct pldm_msgbuf _buf;
+	struct pldm_msgbuf *buf = &_buf;
+	int rc;
+
+	if (!iter || !iter->field || !desc) {
+		return -EINVAL;
+	}
+
+	rc = pldm_msgbuf_init_errno(buf, PLDM_FWUP_DEVICE_DESCRIPTOR_MIN_LEN,
+				    iter->field->ptr, iter->field->length);
+	if (rc) {
+		return rc;
+	}
+
+	pldm_msgbuf_extract(buf, desc->descriptor_type);
+	rc = pldm_msgbuf_extract(buf, desc->descriptor_length);
+	if (rc) {
+		return rc;
+	}
+
+	desc->descriptor_data = NULL;
+	pldm_msgbuf_span_required(buf, desc->descriptor_length,
+				  (void **)&desc->descriptor_data);
+	iter->field->ptr = NULL;
+	pldm_msgbuf_span_remaining(buf, (void **)&iter->field->ptr,
+				   &iter->field->length);
+
+	return pldm_msgbuf_destroy(buf);
+}
+
 LIBPLDM_ABI_STABLE
 int decode_descriptor_type_length_value(const uint8_t *data, size_t length,
 					uint16_t *descriptor_type,
@@ -998,13 +1032,14 @@
 int decode_query_downstream_identifiers_resp(
 	const struct pldm_msg *msg, size_t payload_length,
 	struct pldm_query_downstream_identifiers_resp *resp_data,
-	struct variable_field *downstream_devices)
+	struct pldm_downstream_device_iter *iter)
 {
 	struct pldm_msgbuf _buf;
 	struct pldm_msgbuf *buf = &_buf;
+	void *remaining = NULL;
 	int rc = PLDM_ERROR;
 
-	if (msg == NULL || resp_data == NULL || downstream_devices == NULL ||
+	if (msg == NULL || resp_data == NULL || iter == NULL ||
 	    !payload_length) {
 		return PLDM_ERROR_INVALID_DATA;
 	}
@@ -1036,23 +1071,53 @@
 	}
 
 	pldm_msgbuf_extract(buf, resp_data->number_of_downstream_devices);
-	rc = pldm_msgbuf_span_required(buf,
-				       resp_data->downstream_devices_length,
-				       (void **)&downstream_devices->ptr);
+	rc = pldm_msgbuf_span_required(
+		buf, resp_data->downstream_devices_length, &remaining);
 	if (rc) {
 		return pldm_xlate_errno(rc);
 	}
-	downstream_devices->length = resp_data->downstream_devices_length;
 
 	rc = pldm_msgbuf_destroy(buf);
 	if (rc) {
 		return pldm_xlate_errno(rc);
 	}
 
+	iter->field.ptr = remaining;
+	iter->field.length = resp_data->downstream_devices_length;
+	iter->devs = resp_data->number_of_downstream_devices;
+
 	return PLDM_SUCCESS;
 }
 
 LIBPLDM_ABI_TESTING
+int decode_pldm_downstream_device_from_iter(
+	struct pldm_downstream_device_iter *iter,
+	struct pldm_downstream_device *dev)
+{
+	struct pldm_msgbuf _buf;
+	struct pldm_msgbuf *buf = &_buf;
+	int rc;
+
+	if (!iter || !dev) {
+		return -EINVAL;
+	}
+
+	rc = pldm_msgbuf_init_errno(buf, 3, iter->field.ptr,
+				    iter->field.length);
+	if (rc) {
+		return rc;
+	}
+
+	pldm_msgbuf_extract(buf, dev->downstream_device_index);
+	pldm_msgbuf_extract(buf, dev->downstream_descriptor_count);
+	iter->field.ptr = NULL;
+	pldm_msgbuf_span_remaining(buf, (void **)&iter->field.ptr,
+				   &iter->field.length);
+
+	return pldm_msgbuf_destroy(buf);
+}
+
+LIBPLDM_ABI_TESTING
 int encode_get_downstream_firmware_params_req(
 	uint8_t instance_id, uint32_t data_transfer_handle,
 	enum transfer_op_flag transfer_operation_flag, struct pldm_msg *msg,