From: Xing Tong Wu <xingtong.wu@siemens.com>

Setting the fan speed is only valid in manual mode; it is not possible
to set the fan's speed in automatic mode.
Return error when attempting to set the fan speed in automatic mode.

Signed-off-by: Xing Tong Wu <xingtong.wu@siemens.com>
---
 drivers/hwmon/nct6775-core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/hwmon/nct6775-core.c b/drivers/hwmon/nct6775-core.c
index c24b2c312911..38c2e5b7cfe9 100644
--- a/drivers/hwmon/nct6775-core.c
+++ b/drivers/hwmon/nct6775-core.c
@@ -2556,6 +2556,13 @@ store_pwm(struct device *dev, struct device_attribute *attr, const char *buf,
 	int err;
 	u16 reg;
 
+	/*
+	 * The fan control mode should be set to manual if the user wants to adjust
+	 * the fan speed. Otherwise, it will fail to set.
+	 */
+	if (index == 0 && data->pwm_enable[nr] > manual)
+		return -EBUSY;
+
 	err = kstrtoul(buf, 10, &val);
 	if (err < 0)
 		return err;
-- 
2.25.1