Add update agent interface

Create interface which represents "Firmware Store Update ABI" of the
Platform Security Firmware Update for the A-profile Arm Architecture.
This interface aims for allowing the firmware update provider to use
different implementations of firmware store.

Signed-off-by: Imre Kis <imre.kis@arm.com>
Change-Id: Ie8ec56094e37ab8d75f09e50a6bc6c636b83af1a
diff --git a/components/service/fwu/common/update_agent_interface.h b/components/service/fwu/common/update_agent_interface.h
new file mode 100644
index 0000000..0068908
--- /dev/null
+++ b/components/service/fwu/common/update_agent_interface.h
@@ -0,0 +1,215 @@
+/*
+ * Copyright (c) 2024, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef UPDATE_AGENT_INTERFACE_H
+#define UPDATE_AGENT_INTERFACE_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "common/uuid/uuid.h"
+#include "protocols/service/fwu/packed-c/status.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define FWU_OP_TYPE_READ	(0)
+#define FWU_OP_TYPE_WRITE	(1)
+
+#define FWU_FLAG_PARTIAL_UPDATE	(0x01)
+
+struct fwu_discovery_result {
+	int16_t service_status;
+	uint8_t version_major;
+	uint8_t version_minor;
+	uint64_t max_payload_size;
+	uint32_t flags;
+	uint32_t vendor_specific_flags;
+};
+
+struct update_agent_interface {
+	/**
+	 * \brief Discovery
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[out] result          Discovery result structure
+	 *
+	 * \return 0 on success
+	 */
+	int (*discover)(void *context, struct fwu_discovery_result *result);
+
+	/**
+	 * \brief Begin staging
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  vendor_flags    Vendor specific staging flags
+	 * \param[in]  partial_update_count     Number of update_guid elements
+	 * \param[in]  update_guid     Images to update
+	 *
+	 *
+	 * \return 0 on successfully transitioning to the STAGING state
+	 */
+	int (*begin_staging)(void *context, uint32_t vendor_flags, uint32_t partial_update_count,
+			     const struct uuid_octets *update_guid);
+
+	/**
+	 * \brief End staging
+	 *
+	 * \param[in]  context         The update_agent context
+	 *
+	 * \return 0 on successfully transitioning to the TRIAL state
+	 */
+	int (*end_staging)(void *context);
+
+	/**
+	 * \brief Cancel staging
+	 *
+	 * \param[in]  context         The update_agent context
+	 *
+	 * \return 0 on successfully transitioning to the REGULAR state
+	 */
+	int (*cancel_staging)(void *context);
+
+	/**
+	 * \brief Open a stream for accessing an fwu stream
+	 *
+	 * Used for reading or writing data for accessing images or other fwu
+	 * related objects.
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  uuid            Identifies the object to access
+	 * \param[in]  op_type         Read/write operation, use FWU_OP_TYPE_* macros
+	 * \param[out] handle          For subsequent read/write operations
+	 *
+	 * \return 0 on success
+	 */
+	int (*open)(void *context, const struct uuid_octets *uuid, uint8_t op_type,
+		    uint32_t *handle);
+
+	/**
+	 * \brief Write to a previously opened stream
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  handle          The handle returned by open
+	 * \param[in]  data            Pointer to data
+	 * \param[in]  data_len        The data length
+	 *
+	 * \return 0 on success
+	 */
+	int (*write_stream)(void *context, uint32_t handle, const uint8_t *data, size_t data_len);
+
+	/**
+	 * \brief Read from a previously opened stream
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  handle          The handle returned by open
+	 * \param[in]  buf             Pointer to buffer to copy to
+	 * \param[in]  buf_size        The size of the buffer
+	 * \param[out] read_len        The length of data read
+	 * \param[out] total_len       The total length of the object to read
+	 *
+	 * \return 0 on success
+	 */
+	int (*read_stream)(void *context, uint32_t handle, uint8_t *buf, size_t buf_size,
+			   size_t *read_len, size_t *total_len);
+
+	/**
+	 * \brief Close a stream and commit any writes to the stream
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  handle          The handle returned by open
+	 * \param[in]  accepted        Initial accepted state of an image
+	 * \param[in]  max_atomic_len  Hint, maximum time (in ns) that the Update Agent can execute
+	 *                             continuously without yielding back to the Client. A value of
+	 *                             0 means that the Update Agent can execute for an unbounded
+	 *                             time.
+	 * \param[in]  progress        Units of work already completed by the Update Agent
+	 * \param[in]  total_work      Units of work the Update Agent must perform until fwu_commit
+	 *                             returns successfully
+	 *
+	 * \return 0 on success
+	 */
+	int (*commit)(void *context, uint32_t handle, bool accepted, uint32_t max_atomic_len, uint32_t *progress,
+		      uint32_t *total_work);
+
+
+	/**
+	 * \brief Accept an updated image
+	 *
+	 * \param[in]  context         The update_agent context
+	 * \param[in]  image_type_uuid Identifies the image to accept
+	 *
+	 * \return 0 on success
+	 */
+	int (*accept_image)(void *context, const struct uuid_octets *image_type_uuid);
+
+	/**
+	 * \brief Select previous version
+	 *
+	 *  Revert to a previous good version (if possible).
+	 *
+	 * \param[in]  context         The update_agent context
+	 *
+	 * \return 0 on success
+	 */
+	int (*select_previous)(void *context);
+};
+
+/**
+ * \brief Common update agent instance
+ *
+ * Used by the FWU provider make an association with an agent.
+ */
+struct update_agent {
+	/**
+	 * \brief The update_agent context
+	 *
+	 * Points to backend specific instance data.
+	 */
+	void *context;
+
+	/**
+	 * \brief The update agent interface
+	 *
+	 * A concrete agent provides an implementation of this interface.
+	 */
+	const struct update_agent_interface *interface;
+};
+
+int update_agent_discover(struct update_agent *update_agent, struct fwu_discovery_result *result);
+
+int update_agent_begin_staging(struct update_agent *update_agent, uint32_t vendor_flags,
+			       uint32_t partial_update_count,
+			       const struct uuid_octets *update_guid);
+
+int update_agent_end_staging(struct update_agent *update_agent);
+
+int update_agent_cancel_staging(struct update_agent *update_agent);
+
+int update_agent_open(struct update_agent *update_agent, const struct uuid_octets *uuid,
+		      uint8_t op_type, uint32_t *handle);
+
+int update_agent_write_stream(struct update_agent *update_agent, uint32_t handle,
+			      const uint8_t *data, size_t data_len);
+
+int update_agent_read_stream(struct update_agent *update_agent, uint32_t handle, uint8_t *buf,
+			     size_t buf_size, size_t *read_len, size_t *total_len);
+
+int update_agent_commit(struct update_agent *update_agent, uint32_t handle, bool accepted,
+			uint32_t max_atomic_len, uint32_t *progress, uint32_t *total_work);
+
+int update_agent_accept_image(struct update_agent *update_agent,
+			      const struct uuid_octets *image_type_uuid);
+
+int update_agent_select_previous(struct update_agent *update_agent);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UPDATE_AGENT_INTERFACE_H */