i2c: testunit: improve error handling for GPIO

Bail out in probe if getting the optional GPIO returns an error. Bail
out in the test early if the optional GPIO is not present, otherwise the
timeout errno is misleading.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Author: Wolfram Sang

drivers/i2c/i2c-slave-testunit.c

@@ -183,6 +183,10 @@ static void i2c_slave_testunit_work(struct work_struct *work)
 		break;
 
 	case TU_CMD_SMBUS_ALERT_REQUEST:
+		if (!tu->gpio) {
+			ret = -ENOENT;
+			break;
+		}
 		i2c_slave_unregister(tu->client);
 		orig_addr = tu->client->addr;
 		tu->client->addr = 0x0c;
@@ -232,6 +236,9 @@ static int i2c_slave_testunit_probe(struct i2c_client *client)
 	INIT_DELAYED_WORK(&tu->worker, i2c_slave_testunit_work);
 
 	tu->gpio = devm_gpiod_get_index_optional(&client->dev, NULL, 0, GPIOD_OUT_LOW);
+	if (IS_ERR(tu->gpio))
+		return PTR_ERR(tu->gpio);
+
 	if (gpiod_cansleep(tu->gpio)) {
 		dev_err(&client->dev, "GPIO access which may sleep is not allowed\n");
 		return -EDEADLK;