platform/chrome: cros_ec_proto: add Kunit test for empty payload

cros_ec_wait_until_complete() sends EC_CMD_GET_COMMS_STATUS which expects
to receive sizeof(struct ec_response_get_comms_status) from
cros_ec_xfer_command().

Add Kunit test and expect to receive an error code when
cros_ec_xfer_command() returns 0.

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20220718050914.2267370-10-tzungbi@kernel.org

Author: Tzung-Bi Shih

drivers/platform/chrome/cros_ec_proto_test.c

@@ -1934,6 +1934,36 @@ static void cros_ec_proto_test_cmd_xfer_in_progress_return_error(struct kunit *t
 	KUNIT_EXPECT_EQ(test, cros_kunit_ec_pkt_xfer_mock_called, 2);
 }
 
+static void cros_ec_proto_test_cmd_xfer_in_progress_return0(struct kunit *test)
+{
+	struct cros_ec_proto_test_priv *priv = test->priv;
+	struct cros_ec_device *ec_dev = &priv->ec_dev;
+	struct ec_xfer_mock *mock;
+	int ret;
+	struct cros_ec_command msg;
+
+	memset(&msg, 0, sizeof(msg));
+
+	ec_dev->pkt_xfer = cros_kunit_ec_pkt_xfer_mock;
+
+	/* For the first host command to return EC_RES_IN_PROGRESS. */
+	{
+		mock = cros_kunit_ec_xfer_mock_addx(test, 0, EC_RES_IN_PROGRESS, 0);
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+	}
+
+	/* For EC_CMD_GET_COMMS_STATUS. */
+	{
+		mock = cros_kunit_ec_xfer_mock_add(test, 0);
+		KUNIT_ASSERT_PTR_NE(test, mock, NULL);
+	}
+
+	ret = cros_ec_cmd_xfer(ec_dev, &msg);
+	KUNIT_EXPECT_EQ(test, ret, -EPROTO);
+
+	KUNIT_EXPECT_EQ(test, cros_kunit_ec_pkt_xfer_mock_called, 2);
+}
+
 static void cros_ec_proto_test_release(struct device *dev)
 {
 }
@@ -2013,6 +2043,7 @@ static struct kunit_case cros_ec_proto_test_cases[] = {
 	KUNIT_CASE(cros_ec_proto_test_cmd_xfer_in_progress_retries_status_processing),
 	KUNIT_CASE(cros_ec_proto_test_cmd_xfer_in_progress_xfer_error),
 	KUNIT_CASE(cros_ec_proto_test_cmd_xfer_in_progress_return_error),
+	KUNIT_CASE(cros_ec_proto_test_cmd_xfer_in_progress_return0),
 	{}
 };