tests: canbus: isotp: conformance: add mode_check test

Add a test to check error codes if attempting to use ISO-TP with CAN FD
mode even though the controller supports classical CAN only.

Signed-off-by: Martin Jäger <martin@libre.solar>

tests/subsys/canbus/isotp/conformance/src/mode_check.c

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2023 Libre Solar Technologies GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This test suite checks that correct errors are returned when trying to use the ISO-TP
+ * protocol with CAN-FD mode even though the controller does not support CAN-FD.
+ */
+
+#include <zephyr/canbus/isotp.h>
+#include <zephyr/ztest.h>
+
+static const struct device *const can_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_canbus));
+static struct isotp_recv_ctx recv_ctx;
+static struct isotp_send_ctx send_ctx;
+static bool canfd_capable;
+
+static const struct isotp_fc_opts fc_opts = {
+	.bs = 0,
+	.stmin = 0
+};
+
+static const struct isotp_msg_id rx_addr = {
+	.std_id = 0x20,
+#ifdef CONFIG_TEST_USE_CAN_FD_MODE
+	.dl = CONFIG_TEST_ISOTP_TX_DL,
+	.flags = ISOTP_MSG_FDF | ISOTP_MSG_BRS,
+#endif
+};
+
+static const struct isotp_msg_id tx_addr = {
+	.std_id = 0x21,
+#ifdef CONFIG_TEST_USE_CAN_FD_MODE
+	.dl = CONFIG_TEST_ISOTP_TX_DL,
+	.flags = ISOTP_MSG_FDF | ISOTP_MSG_BRS,
+#endif
+};
+
+ZTEST(isotp_canfd_notsup, test_bind)
+{
+	int err;
+
+	err = isotp_bind(&recv_ctx, can_dev, &rx_addr, &tx_addr, &fc_opts, K_NO_WAIT);
+	if (IS_ENABLED(CONFIG_TEST_USE_CAN_FD_MODE) && !canfd_capable) {
+		zassert_equal(err, ISOTP_N_ERROR);
+	} else {
+		zassert_equal(err, ISOTP_N_OK);
+	}
+
+	isotp_unbind(&recv_ctx);
+}
+
+ZTEST(isotp_canfd_notsup, test_send)
+{
+	uint8_t buf[] = { 1, 2, 3 };
+	int err;
+
+	err = isotp_send(&send_ctx, can_dev, buf, sizeof(buf), &rx_addr, &tx_addr, NULL, NULL);
+	if (IS_ENABLED(CONFIG_TEST_USE_CAN_FD_MODE) && !canfd_capable) {
+		zassert_equal(err, ISOTP_N_ERROR);
+	} else {
+		zassert_equal(err, ISOTP_N_OK);
+	}
+}
+
+static void *isotp_canfd_notup_setup(void)
+{
+	can_mode_t cap;
+	int err;
+
+	zassert_true(device_is_ready(can_dev), "CAN device not ready");
+
+	err = can_get_capabilities(can_dev, &cap);
+	zassert_equal(err, 0, "failed to get CAN controller capabilities (err %d)", err);
+
+	canfd_capable = (cap & CAN_MODE_FD) != 0;
+
+	(void)can_stop(can_dev);
+
+	err = can_set_mode(can_dev, CAN_MODE_LOOPBACK | (canfd_capable ? CAN_MODE_FD : 0));
+	zassert_equal(err, 0, "Failed to set mode [%d]", err);
+
+	err = can_start(can_dev);
+	zassert_equal(err, 0, "Failed to start CAN controller [%d]", err);
+
+	return NULL;
+}
+
+ZTEST_SUITE(isotp_canfd_notsup, NULL, isotp_canfd_notup_setup, NULL, NULL, NULL);