rtc: rx8010: don't modify the global rtc ops

The way the driver is implemented is buggy for the (admittedly unlikely)
use case where there are two RTCs with one having an interrupt configured
and the second not. This is caused by the fact that we use a global
rtc_class_ops struct which we modify depending on whether the irq number
is present or not.

Fix it by using two const ops structs with and without alarm operations.
While at it: not being able to request a configured interrupt is an error
so don't ignore it and bail out of probe().

Fixes: ed13d89b ("rtc: Add Epson RX8010SJ RTC driver")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200914154601.32245-2-brgl@bgdev.pl

drivers/rtc/rtc-rx8010.c

@@ -407,16 +407,26 @@ static int rx8010_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 	}
 }
 
-static struct rtc_class_ops rx8010_rtc_ops = {
+static const struct rtc_class_ops rx8010_rtc_ops_default = {
 	.read_time = rx8010_get_time,
 	.set_time = rx8010_set_time,
 	.ioctl = rx8010_ioctl,
 };
 
+static const struct rtc_class_ops rx8010_rtc_ops_alarm = {
+	.read_time = rx8010_get_time,
+	.set_time = rx8010_set_time,
+	.ioctl = rx8010_ioctl,
+	.read_alarm = rx8010_read_alarm,
+	.set_alarm = rx8010_set_alarm,
+	.alarm_irq_enable = rx8010_alarm_irq_enable,
+};
+
 static int rx8010_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
 	struct i2c_adapter *adapter = client->adapter;
+	const struct rtc_class_ops *rtc_ops;
 	struct rx8010_data *rx8010;
 	int err = 0;
 
@@ -447,16 +457,16 @@ static int rx8010_probe(struct i2c_client *client,
 
 		if (err) {
 			dev_err(&client->dev, "unable to request IRQ\n");
-			client->irq = 0;
-		} else {
-			rx8010_rtc_ops.read_alarm = rx8010_read_alarm;
-			rx8010_rtc_ops.set_alarm = rx8010_set_alarm;
-			rx8010_rtc_ops.alarm_irq_enable = rx8010_alarm_irq_enable;
+			return err;
 		}
+
+		rtc_ops = &rx8010_rtc_ops_alarm;
+	} else {
+		rtc_ops = &rx8010_rtc_ops_default;
 	}
 
 	rx8010->rtc = devm_rtc_device_register(&client->dev, client->name,
-		&rx8010_rtc_ops, THIS_MODULE);
+					       rtc_ops, THIS_MODULE);
 
 	if (IS_ERR(rx8010->rtc)) {
 		dev_err(&client->dev, "unable to register the class device\n");