hwmon: (core) Simplify sysfs attribute name allocation

Allocating the sysfs attribute name only if needed and only with the
required minimum length looks optimal, but does not take the additional
overhead for both devm_ data structures and the allocation header itself
into account. This also results in unnecessary memory fragmentation.
Move the sysfs name string into struct hwmon_device_attribute and give it
a sufficient length to reduce this overhead.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -38,12 +38,15 @@ struct hwmon_device {
 
 #define to_hwmon_device(d) container_of(d, struct hwmon_device, dev)
 
+#define MAX_SYSFS_ATTR_NAME_LENGTH	32
+
 struct hwmon_device_attribute {
 	struct device_attribute dev_attr;
 	const struct hwmon_ops *ops;
 	enum hwmon_sensor_types type;
 	u32 attr;
 	int index;
+	char name[MAX_SYSFS_ATTR_NAME_LENGTH];
 };
 
 #define to_hwmon_attr(d) \
@@ -261,20 +264,18 @@ static struct attribute *hwmon_genattr(struct device *dev,
 	if ((mode & S_IWUGO) && !ops->write)
 		return ERR_PTR(-EINVAL);
 
+	hattr = devm_kzalloc(dev, sizeof(*hattr), GFP_KERNEL);
+	if (!hattr)
+		return ERR_PTR(-ENOMEM);
+
 	if (type == hwmon_chip) {
 		name = (char *)template;
 	} else {
-		name = devm_kzalloc(dev, strlen(template) + 16, GFP_KERNEL);
-		if (!name)
-			return ERR_PTR(-ENOMEM);
-		scnprintf(name, strlen(template) + 16, template,
+		scnprintf(hattr->name, sizeof(hattr->name), template,
 			  index + hwmon_attr_base(type));
+		name = hattr->name;
 	}
 
-	hattr = devm_kzalloc(dev, sizeof(*hattr), GFP_KERNEL);
-	if (!hattr)
-		return ERR_PTR(-ENOMEM);
-
 	hattr->type = type;
 	hattr->attr = attr;
 	hattr->index = index;