Interface: Update PSA Protected Storage header comments

This patch adds comments for documentation purposes
to the psa/protected_storage.h header

Change-Id: Ic7294a675f68f8f5e598cd5beacf5ebab7ec1740
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/interface/include/psa/protected_storage.h b/interface/include/psa/protected_storage.h
index f27c53f..e76205c 100644
--- a/interface/include/psa/protected_storage.h
+++ b/interface/include/psa/protected_storage.h
@@ -20,14 +20,50 @@
 extern "C" {
 #endif
 
+/**
+ * \brief PSA_PS_API_VERSION version
+ *
+ * Major and minor PSA_PS_API_VERSION numbers
+ */
 #define PSA_PS_API_VERSION_MAJOR  1
 #define PSA_PS_API_VERSION_MINOR  0
 
-// This version of the header file is associated with 1.0 final release.
+// This version of the header file is associated with 1.0 final release
 
 /**
- * Create a new or modify an existing key/value pair
+ * \brief Create a new, or modify an existing, uid/value pair
  *
+ * Stores data in the protected storage.
+ *
+ * \param[in] uid           The identifier for the data
+ * \param[in] data_length   The size in bytes of the data in `p_data`
+ * \param[in] p_data        A buffer containing the data
+ * \param[in] create_flags  The flags that the data will be stored with
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                     The operation completed successfully
+ * \retval PSA_ERROR_NOT_PERMITTED         The operation failed because the
+ *                                         provided `uid` value was already
+ *                                         created with
+ *                                         PSA_STORAGE_FLAG_WRITE_ONCE
+ * \retval PSA_ERROR_INVALID_ARGUMENT      The operation failed because one
+ *                                         of the provided pointers(`p_data`)
+ *                                         is invalid, for example is `NULL` or
+ *                                         references memory the caller cannot
+ *                                         access
+ * \retval PSA_ERROR_NOT_SUPPORTED         The operation failed because one or
+ *                                         more of the flags provided in
+ *                                         `create_flags` is not supported or is
+ *                                         not valid
+ * \retval PSA_ERROR_INSUFFICIENT_STORAGE  The operation failed because there
+ *                                         was insufficient space on the
+ *                                         storage medium
+ * \retval PSA_ERROR_STORAGE_FAILURE       The operation failed because the
+ *                                         physical storage has failed (Fatal
+ *                                         error)
+ * \retval PSA_ERROR_GENERIC_ERROR         The operation failed because of an
+ *                                         unspecified internal failure
  */
 psa_status_t psa_ps_set(psa_storage_uid_t uid,
                         size_t data_length,
@@ -35,7 +71,47 @@
                         psa_storage_create_flags_t create_flags);
 
 /**
- * Retrieve data associated with a provided UID
+ * \brief Retrieve data associated with a provided uid
+ *
+ * Retrieves up to `data_size` bytes of the data associated with `uid`, starting
+ * at `data_offset` bytes from the beginning of the data. Upon successful
+ * completion, the data will be placed in the `p_data` buffer, which must be at
+ * least `data_size` bytes in size. The length of the data returned will be in
+ * `p_data_length`. If `data_size` is 0, the contents of `p_data_length` will
+ * be set to zero.
+ *
+ * \param[in]  uid            The uid value
+ * \param[in]  data_offset    The starting offset of the data requested
+ * \param[in]  data_size      The amount of data requested
+ * \param[out] p_data         On success, the buffer where the data will
+ *                            be placed
+ * \param[out] p_data_length  On success, this will contain size of the data
+ *                            placed in `p_data`
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                 The operation completed successfully
+ * \retval PSA_ERROR_INVALID_ARGUMENT  The operation failed because one of the
+ *                                     provided arguments (`p_data`,
+ *                                     `p_data_length`) is invalid, for example
+ *                                     is `NULL` or references memory the
+ *                                     caller cannot access. In addition, this
+ *                                     can also happen if `data_offset` is
+ *                                     larger than the size of the data
+ *                                     associated with `uid`
+ * \retval PSA_ERROR_DOES_NOT_EXIST    The operation failed because the
+ *                                     provided `uid` value was not found in
+ *                                     the storage
+ * \retval PSA_ERROR_STORAGE_FAILURE   The operation failed because the
+ *                                     physical storage has failed (Fatal
+ *                                     error)
+ * \retval PSA_ERROR_GENERIC_ERROR     The operation failed because of an
+ *                                     unspecified internal failure
+ * \retval PSA_ERROR_DATA_CORRUPT      The operation failed because the data
+ *                                     associated with the UID was corrupt
+ * \retval PSA_ERROR_INVALID_SIGNATURE The operation failed because the data
+ *                                     associated with the UID failed
+ *                                     authentication
  */
 psa_status_t psa_ps_get(psa_storage_uid_t uid,
                         size_t data_offset,
@@ -44,26 +120,144 @@
                         size_t *p_data_length);
 
 /**
- * Retrieve the metadata about the provided uid
+ * \brief Retrieve the metadata about the provided uid
+ *
+ * Retrieves the metadata stored for a given `uid`
+ *
+ * \param[in]  uid     The `uid` value
+ * \param[out] p_info  A pointer to the `psa_storage_info_t` struct that will
+ *                     be populated with the metadata
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                 The operation completed successfully
+ * \retval PSA_ERROR_INVALID_ARGUMENT  The operation failed because one of the
+ *                                     provided pointers(`p_info`)
+ *                                     is invalid, for example is `NULL` or
+ *                                     references memory the caller cannot
+ *                                     access
+ * \retval PSA_ERROR_DOES_NOT_EXIST    The operation failed because the provided
+ *                                     uid value was not found in the storage
+ * \retval PSA_ERROR_STORAGE_FAILURE   The operation failed because the physical
+ *                                     storage has failed (Fatal error)
+ * \retval PSA_ERROR_GENERIC_ERROR     The operation failed because of an
+ *                                     unspecified internal failure
+ * \retval PSA_ERROR_DATA_CORRUPT      The operation failed because the data
+ *                                     associated with the UID was corrupt
  */
 psa_status_t psa_ps_get_info(psa_storage_uid_t uid,
                              struct psa_storage_info_t *p_info);
 
 /**
- * Remove the provided uid and its associated data from the storage
+ * \brief Remove the provided uid and its associated data from the storage
+ *
+ * Removes previously stored data and any associated metadata,
+ * including rollback protection data.
+ *
+ * \param[in] uid  The `uid` value
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                 The operation completed successfully
+ * \retval PSA_ERROR_INVALID_ARGUMENT  The operation failed because one or more
+ *                                     of the given arguments were invalid (null
+ *                                     pointer, wrong flags and so on)
+ * \retval PSA_ERROR_DOES_NOT_EXIST    The operation failed because the provided
+ *                                     uid value was not found in the storage
+ * \retval PSA_ERROR_NOT_PERMITTED     The operation failed because the provided
+ *                                     uid value was created with
+ *                                     PSA_STORAGE_FLAG_WRITE_ONCE
+ * \retval PSA_ERROR_STORAGE_FAILURE   The operation failed because the physical
+ *                                     storage has failed (Fatal error)
+ * \retval PSA_ERROR_GENERIC_ERROR     The operation failed because of an
+ *                                     unspecified internal failure
  */
 psa_status_t psa_ps_remove(psa_storage_uid_t uid);
 
 /**
- * Reserves storage for the specified UID.
+ * \brief Reserves storage for the specified uid
+ *
+ * Upon success, the capacity of the storage will be capacity, and the size
+ * will be 0. It is only necessary to call this function for assets that will
+ * be written with the psa_ps_set_extended function. If only the psa_ps_set
+ * function is needed, calls to this function are redundant.
+ *
+ * \param[in] uid           The `uid` value
+ * \param[in] capacity      The capacity to be allocated in bytes
+ * \param[in] create_flags  Flags indicating properties of storage
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                     The operation completed successfully
+ * \retval PSA_ERROR_STORAGE_FAILURE       The operation failed because the
+ *                                         physical storage has failed
+ *                                         (Fatal error)
+ * \retval PSA_ERROR_INSUFFICIENT_STORAGE  The operation failed because the
+ *                                         capacity is bigger than the current
+ *                                         available space
+ * \retval PSA_ERROR_NOT_SUPPORTED         The operation failed because the
+ *                                         function is not implemented or one
+ *                                         or more create_flags are not
+ *                                         supported.
+ * \retval PSA_ERROR_INVALID_ARGUMENT      The operation failed because uid was
+ *                                         0 or create_flags specified flags
+ *                                         that are not defined in the API.
+ * \retval PSA_ERROR_GENERIC_ERROR         The operation failed due to an
+ *                                         unspecified error
+ * \retval PSA_ERROR_ALREADY_EXISTS        Storage for the specified uid
+ *                                         already exists
  */
 psa_status_t psa_ps_create(psa_storage_uid_t uid,
                            size_t capacity,
                            psa_storage_create_flags_t create_flags);
 
 /**
- * Sets partial data into an asset based on the given identifier, data_offset,
- * data length and p_data.
+ * \brief Sets partial data into an asset
+ *
+ * Before calling this function, the storage must have been reserved with a call
+ * to psa_ps_create. It can also be used to overwrite data in an asset that was
+ * created with a call to psa_ps_set. Calling this function with data_length = 0
+ * is permitted, which will make no change to the stored data.This function can
+ * overwrite existing data and/or extend it up to the capacity for the uid
+ * specified in psa_ps_create, but cannot create gaps.
+ *
+ * That is, it has preconditions:
+ * - data_offset <= size
+ * - data_offset + data_length <= capacity
+ * and postconditions:
+ * - size = max(size, data_offset + data_length)
+ * - capacity unchanged.
+ *
+ * \param[in] uid          The `uid` value
+ * \param[in] data_offset  Offset within the asset to start the write
+ * \param[in] data_length  The size in bytes of the data in p_data to write
+ * \param[in] p_data       Pointer to a buffer which contains the data to write
+ *
+ * \return A status indicating the success/failure of the operation
+ *
+ * \retval PSA_SUCCESS                  The asset exists, the input parameters
+ *                                      are correct and the data is correctly
+ *                                      written in the physical storage.
+ * \retval PSA_ERROR_STORAGE_FAILURE    The data was not written correctly in
+ *                                      the physical storage
+ * \retval PSA_ERROR_INVALID_ARGUMENT   The operation failed because one or more
+ *                                      of the preconditions listed above
+ *                                      regarding data_offset, size, or
+ *                                      data_length was violated.
+ * \retval PSA_ERROR_DOES_NOT_EXIST     The specified uid was not found
+ * \retval PSA_ERROR_NOT_SUPPORTED      The implementation of the API does not
+ *                                      support this function
+ * \retval PSA_ERROR_GENERIC_ERROR      The operation failed due to an
+ *                                      unspecified error
+ * \retval PSA_ERROR_DATA_CORRUPT       The operation failed because the
+ *                                      existing data has been corrupted.
+ * \retval PSA_ERROR_INVALID_SIGNATURE  The operation failed because the
+ *                                      existing data failed authentication
+ *                                      (MAC check failed).
+ * \retval PSA_ERROR_NOT_PERMITTED      The operation failed because it was
+ *                                      attempted on an asset which was written
+ *                                      with the flag
+ *                                      PSA_STORAGE_FLAG_WRITE_ONCE
  */
 psa_status_t psa_ps_set_extended(psa_storage_uid_t uid,
                                  size_t data_offset,
@@ -71,9 +265,13 @@
                                  const void *p_data);
 
 /**
- * Returns a bitmask with flags set for all of the optional features supported
- * by the implementation.
+ * \brief Lists optional features.
  *
+ * \return                              A bitmask with flags set for all of
+ *                                      the optional features supported by the
+ *                                      implementation.Currently defined flags
+ *                                      are limited to
+ *                                      PSA_STORAGE_SUPPORT_SET_EXTENDED
  */
 uint32_t psa_ps_get_support(void);
 
@@ -81,4 +279,4 @@
 }
 #endif
 
-#endif // PSA_PROTECTED_STORAGE_H
+#endif /* PSA_PROTECTED_STORAGE_H */