mbedtls_ecp_write_key_ext: document error for no private key set
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 05778cd..e2ae074 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -1392,6 +1392,8 @@
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL if the \p key
* representation is larger than the available space in \p buf.
+ * \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if no private key is
+ * set in \p key.
* \return Another negative error code on different kinds of failure.
*/
int mbedtls_ecp_write_key_ext(mbedtls_ecp_keypair *key,