pmbus: support for custom sysfs attributes

This patch makes it possible to pass custom struct attribute_group array
via the pmbus_driver_info struct so that those can be added to the
attribute groups passed to hwmon_device_register_with_groups().

This makes it possible to register custom sysfs attributes by PMBUS
drivers similar to how you can do this with most other busses/classes.
Signed-off-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/pmbus.h

@@ -432,6 +432,9 @@ struct pmbus_driver_info {
 	/* Regulator functionality, if supported by this chip driver. */
 	int num_regulators;
 	const struct regulator_desc *reg_desc;
+
+	/* custom attributes */
+	const struct attribute_group **groups;
 };
 
 /* Regulator ops */

drivers/hwmon/pmbus/pmbus_core.c

@@ -103,7 +103,7 @@ struct pmbus_data {
 	int max_attributes;
 	int num_attributes;
 	struct attribute_group group;
-	const struct attribute_group *groups[2];
+	const struct attribute_group **groups;
 	struct dentry *debugfs;		/* debugfs device directory */
 
 	struct pmbus_sensor *sensors;
@@ -2415,6 +2415,7 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
 	struct device *dev = &client->dev;
 	const struct pmbus_platform_data *pdata = dev_get_platdata(dev);
 	struct pmbus_data *data;
+	size_t groups_num = 0;
 	int ret;
 
 	if (!info)
@@ -2429,6 +2430,15 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
 	if (!data)
 		return -ENOMEM;
 
+	if (info->groups)
+		while (info->groups[groups_num])
+			groups_num++;
+
+	data->groups = devm_kcalloc(dev, groups_num + 2, sizeof(void *),
+				    GFP_KERNEL);
+	if (!data->groups)
+		return -ENOMEM;
+
 	i2c_set_clientdata(client, data);
 	mutex_init(&data->update_lock);
 	data->dev = dev;
@@ -2456,6 +2466,7 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
 	}
 
 	data->groups[0] = &data->group;
+	memcpy(data->groups + 1, info->groups, sizeof(void *) * groups_num);
 	data->hwmon_dev = hwmon_device_register_with_groups(dev, client->name,
 							    data, data->groups);
 	if (IS_ERR(data->hwmon_dev)) {