hwmon: (gpio-fan) allow to use alarm support alone from DT

On some boards, such as the LaCie 2Big Network v2 or 2Big NAS (based on
Marvell Kirkwood SoCs), an I2C fan controller is used but the alarm
signal is wired to a separate GPIO. Unfortunately, the gpio-fan driver
can't be used to handle GPIO alarm alone from DT: an error is returned
if the "gpios" DT property is missing.

This patch allows to use the gpio-fan driver even if the "alarm-gpios"
DT property is defined alone.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 23 insertions, 21 deletions

diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
index 36abf814b8c7..c241f5b0b7cf 100644
--- a/drivers/hwmon/gpio-fan.c
+++ b/drivers/hwmon/gpio-fan.c
@@ -404,10 +404,32 @@ static int gpio_fan_get_of_pdata(struct device *dev,
 
 	node = dev->of_node;
 
+	/* Alarm GPIO if one exists */
+	if (of_gpio_named_count(node, "alarm-gpios") > 0) {
+		struct gpio_fan_alarm *alarm;
+		int val;
+		enum of_gpio_flags flags;
+
+		alarm = devm_kzalloc(dev, sizeof(struct gpio_fan_alarm),
+					GFP_KERNEL);
+		if (!alarm)
+			return -ENOMEM;
+
+		val = of_get_named_gpio_flags(node, "alarm-gpios", 0, &flags);
+		if (val < 0)
+			return val;
+		alarm->gpio = val;
+		alarm->active_low = flags & OF_GPIO_ACTIVE_LOW;
+
+		pdata->alarm = alarm;
+	}
+
 	/* Fill GPIO pin array */
 	pdata->num_ctrl = of_gpio_count(node);
 	if (pdata->num_ctrl <= 0) {
-		dev_err(dev, "gpios DT property empty / missing");
+		if (pdata->alarm)
+			return 0;
+		dev_err(dev, "DT properties empty / missing");
 		return -ENODEV;
 	}
 	ctrl = devm_kzalloc(dev, pdata->num_ctrl * sizeof(unsigned),
@@ -460,26 +482,6 @@ static int gpio_fan_get_of_pdata(struct device *dev,
 	}
 	pdata->speed = speed;
 
-	/* Alarm GPIO if one exists */
-	if (of_gpio_named_count(node, "alarm-gpios") > 0) {
-		struct gpio_fan_alarm *alarm;
-		int val;
-		enum of_gpio_flags flags;
-
-		alarm = devm_kzalloc(dev, sizeof(struct gpio_fan_alarm),
-					GFP_KERNEL);
-		if (!alarm)
-			return -ENOMEM;
-
-		val = of_get_named_gpio_flags(node, "alarm-gpios", 0, &flags);
-		if (val < 0)
-			return val;
-		alarm->gpio = val;
-		alarm->active_low = flags & OF_GPIO_ACTIVE_LOW;
-
-		pdata->alarm = alarm;
-	}
-
 	return 0;
 }