hwmon: Add "label" attribute

If a label is defined in the device tree for this device add that
to the device specific attributes. This is useful for userspace to
be able to identify an individual device when multiple identical
chips are present in the system.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Link: https://lore.kernel.org/r/20220110182256.30763-3-paul@crapouillou.netSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -18,6 +18,7 @@
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/thermal.h>
@@ -30,6 +31,7 @@
 
 struct hwmon_device {
 	const char *name;
+	const char *label;
 	struct device dev;
 	const struct hwmon_chip_info *chip;
 	struct list_head tzdata;
@@ -71,17 +73,29 @@ name_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(name);
 
+static ssize_t
+label_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->label);
+}
+static DEVICE_ATTR_RO(label);
+
 static struct attribute *hwmon_dev_attrs[] = {
 	&dev_attr_name.attr,
+	&dev_attr_label.attr,
 	NULL
 };
 
-static umode_t hwmon_dev_name_is_visible(struct kobject *kobj,
+static umode_t hwmon_dev_attr_is_visible(struct kobject *kobj,
 					 struct attribute *attr, int n)
 {
 	struct device *dev = kobj_to_dev(kobj);
+	struct hwmon_device *hdev = to_hwmon_device(dev);
 
-	if (to_hwmon_device(dev)->name == NULL)
+	if (attr == &dev_attr_name.attr && hdev->name == NULL)
+		return 0;
+
+	if (attr == &dev_attr_label.attr && hdev->label == NULL)
 		return 0;
 
 	return attr->mode;
@@ -89,7 +103,7 @@ static umode_t hwmon_dev_name_is_visible(struct kobject *kobj,
 
 static const struct attribute_group hwmon_dev_attr_group = {
 	.attrs		= hwmon_dev_attrs,
-	.is_visible	= hwmon_dev_name_is_visible,
+	.is_visible	= hwmon_dev_attr_is_visible,
 };
 
 static const struct attribute_group *hwmon_dev_attr_groups[] = {
@@ -117,6 +131,7 @@ static void hwmon_dev_release(struct device *dev)
 	if (hwdev->group.attrs)
 		hwmon_free_attrs(hwdev->group.attrs);
 	kfree(hwdev->groups);
+	kfree(hwdev->label);
 	kfree(hwdev);
 }
 
@@ -738,6 +753,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 			const struct attribute_group **groups)
 {
 	struct hwmon_device *hwdev;
+	const char *label;
 	struct device *hdev;
 	int i, err, id;
 
@@ -793,6 +809,18 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 		hdev->groups = groups;
 	}
 
+	if (device_property_present(dev, "label")) {
+		err = device_property_read_string(dev, "label", &label);
+		if (err < 0)
+			goto free_hwmon;
+
+		hwdev->label = kstrdup(label, GFP_KERNEL);
+		if (hwdev->label == NULL) {
+			err = -ENOMEM;
+			goto free_hwmon;
+		}
+	}
+
 	hwdev->name = name;
 	hdev->class = &hwmon_class;
 	hdev->parent = dev;