Update documentation about optional f_rng parameter
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 065a4cc..f2e5916 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -813,6 +813,9 @@
* intermediate results to prevent potential timing attacks
* targeting these results. We recommend always providing
* a non-NULL \p f_rng. The overhead is negligible.
+ * Note: unless #MBEDTLS_ECP_NO_INTERNAL_RNG is defined, when
+ * \p f_rng is NULL, an internal RNG (seeded from the value
+ * of \p m) will be used instead.
*
* \param grp The ECP group to use.
* This must be initialized and have group parameters