Fix formatting and code comments

Signed-off-by: Aditya Deshpande <aditya.deshpande@arm.com>

library/psa_crypto_ecp.c

@@ -468,8 +468,9 @@ cleanup:
 /****************************************************************/
 /* ECDH Key Agreement */
 /****************************************************************/
+
 #if defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH)
-psa_status_t mbedtls_psa_key_agreement_ecdh( 
+psa_status_t mbedtls_psa_key_agreement_ecdh(
     const psa_key_attributes_t *attributes,
     const uint8_t *key_buffer, size_t key_buffer_size,
     psa_algorithm_t alg, const uint8_t *peer_key, size_t peer_key_length,

library/psa_crypto_ecp.h

@@ -219,7 +219,49 @@ psa_status_t mbedtls_psa_ecdsa_verify_hash(
     psa_algorithm_t alg, const uint8_t *hash, size_t hash_length,
     const uint8_t *signature, size_t signature_length );
 
-psa_status_t mbedtls_psa_key_agreement_ecdh( 
+
+/** Perform a key agreement and return the raw ECDH shared secret.
+ *
+ * \note The signature of this function is that of a PSA driver
+ *       key_agreement entry point. This function behaves as a key_agreement
+ *       entry point as defined in the PSA driver interface specification for
+ *       transparent drivers.
+ *
+ * \param[in]  attributes           The attributes of the key to use for the
+ *                                  operation.
+ * \param[in]  key_buffer           The buffer containing the private key
+ *                                  context.
+ * \param[in]  key_buffer_size      Size of the \p key_buffer buffer in
+ *                                  bytes.
+ * \param[in]  alg                  A key agreement algorithm that is
+ *                                  compatible with the type of the key.
+ * \param[in]  peer_key             The buffer containing the key context
+ *                                  of the peer's public key.
+ * \param[in]  peer_key_length      Size of the \p peer_key buffer in
+ *                                  bytes.
+ * \param[out] shared_secret        The buffer to which the shared secret
+ *                                  is to be written.
+ * \param[in]  shared_secret_size   Size of the \p shared_secret buffer in
+ *                                  bytes.
+ * \param[out] shared_secret_length On success, the number of bytes that make
+ *                                  up the returned shared secret.
+ * \retval #PSA_SUCCESS
+ *         Success. Shared secret successfully calculated.
+ * \retval #PSA_ERROR_INVALID_HANDLE
+ * \retval #PSA_ERROR_NOT_PERMITTED
+ * \retval #PSA_ERROR_INVALID_ARGUMENT
+ *         \p alg is not a key agreement algorithm, or
+ *         \p private_key is not compatible with \p alg,
+ *         or \p peer_key is not valid for \p alg or not compatible with
+ *         \p private_key.
+ * \retval #PSA_ERROR_BUFFER_TOO_SMALL
+ *         \p shared_secret_size is too small
+ * \retval #PSA_ERROR_NOT_SUPPORTED
+ *         \p alg is not a supported key agreement algorithm.
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ */
+psa_status_t mbedtls_psa_key_agreement_ecdh(
     const psa_key_attributes_t *attributes,
     const uint8_t *key_buffer, size_t key_buffer_size,
     psa_algorithm_t alg, const uint8_t *peer_key, size_t peer_key_length,

tests/src/drivers/test_driver_key_agreement.c

@@ -82,7 +82,7 @@ psa_status_t mbedtls_test_transparent_key_agreement(
                 alg, peer_key, peer_key_length,
                 shared_secret, shared_secret_size,
                 shared_secret_length ) );
-#endif   
+#endif
     }
     else
     {