Improve doc about length of strings written
diff --git a/include/mbedtls/x509_crl.h b/include/mbedtls/x509_crl.h
index 7b40739..dbc4642 100644
--- a/include/mbedtls/x509_crl.h
+++ b/include/mbedtls/x509_crl.h
@@ -143,8 +143,8 @@
* \param prefix A line prefix
* \param crl The X509 CRL to represent
*
- * \return The amount of data written to the buffer, or -1 in
- * case of an error.
+ * \return The length of the string written (not including the
+ * terminated nul byte), or a negative error code.
*/
int mbedtls_x509_crl_info( char *buf, size_t size, const char *prefix,
const mbedtls_x509_crl *crl );