Add return info to sha256 docs
@@ -167,6 +167,9 @@ int mbedtls_internal_sha256_process( mbedtls_sha256_context *ctx,
* for SHA-256, \c 28 bytes for SHA-224.
* \param is224 Determines which function to use. This must be
* either \c 0 for SHA-256, or \c 1 for SHA-224.
+ *
+ * \return \c 0 on success.
+ * \return A negative error code on failure.
*/
int mbedtls_sha256( const unsigned char *input,
size_t ilen,
