add comment about potential future extension
as requested, see
@@ -311,6 +311,8 @@ int mbedtls_x509_crt_parse_der( mbedtls_x509_crt *chain,
* it encounters either an unsupported extension or a
* "certificate policies" extension containing any
* unsupported certificate policies.
+ * Future versions of the library may invoke the callback
+ * in other cases, if and when the need arises.
*
* \param p_ctx An opaque context passed to the callback.
* \param crt The certificate being parsed.
@@ -372,6 +374,8 @@ typedef int (*mbedtls_x509_crt_ext_cb_t)( void *p_ctx,
* When the callback fails to parse a non critical extension
* mbedtls_x509_crt_parse_der_with_ext_cb() simply skips
* the extension and continues parsing.
+ * Future versions of the library may invoke the callback
+ * in other cases, if and when the need arises.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
