hwmon: Constify str parameter of hwmon_ops->read_string

The read_string callback is supposed to retrieve a pointer to a
constant string.
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -186,7 +186,7 @@ static ssize_t hwmon_attr_show_string(struct device *dev,
 				      char *buf)
 {
 	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
-	char *s;
+	const char *s;
 	int ret;
 
 	ret = hattr->ops->read_string(dev, hattr->type, hattr->attr,

include/linux/hwmon.h

@@ -337,7 +337,7 @@ struct hwmon_ops {
 	int (*read)(struct device *dev, enum hwmon_sensor_types type,
 		    u32 attr, int channel, long *val);
 	int (*read_string)(struct device *dev, enum hwmon_sensor_types type,
-		    u32 attr, int channel, char **str);
+		    u32 attr, int channel, const char **str);
 	int (*write)(struct device *dev, enum hwmon_sensor_types type,
 		     u32 attr, int channel, long val);
 };