thunderbolt: Link USB4 ports to their USB Type-C connectors

Creating a symlink pointing to the correct USB Type-C
connector for the on-board USB4 ports when they are created.
The link will be created only if the firmware is able to
describe the connection between the port and its connector.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Won Chung <wonchung@google.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Documentation/ABI/testing/sysfs-bus-thunderbolt

@@ -293,6 +293,16 @@ Contact:	thunderbolt-software@lists.01.org
 Description:	This contains XDomain service specific settings as
 		bitmask. Format: %x
 
+What:		/sys/bus/thunderbolt/devices/usb4_portX/connector
+Date:		April 2022
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		Symlink to the USB Type-C connector. This link is only
+		created when USB Type-C Connector Class is enabled,
+		and only if the system firmware is capable of
+		describing the connection between a port and its
+		connector.
+
 What:		/sys/bus/thunderbolt/devices/usb4_portX/link
 Date:		Sep 2021
 KernelVersion:	v5.14

drivers/thunderbolt/usb4_port.c

@@ -7,9 +7,37 @@
  */
 
 #include <linux/pm_runtime.h>
+#include <linux/component.h>
+#include <linux/property.h>
 
 #include "tb.h"
 
+static int connector_bind(struct device *dev, struct device *connector, void *data)
+{
+	int ret;
+
+	ret = sysfs_create_link(&dev->kobj, &connector->kobj, "connector");
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_link(&connector->kobj, &dev->kobj, dev_name(dev));
+	if (ret)
+		sysfs_remove_link(&dev->kobj, "connector");
+
+	return ret;
+}
+
+static void connector_unbind(struct device *dev, struct device *connector, void *data)
+{
+	sysfs_remove_link(&connector->kobj, dev_name(dev));
+	sysfs_remove_link(&dev->kobj, "connector");
+}
+
+static const struct component_ops connector_ops = {
+	.bind = connector_bind,
+	.unbind = connector_unbind,
+};
+
 static ssize_t link_show(struct device *dev, struct device_attribute *attr,
 			 char *buf)
 {
@@ -246,6 +274,14 @@ struct usb4_port *usb4_port_device_add(struct tb_port *port)
 		return ERR_PTR(ret);
 	}
 
+	if (dev_fwnode(&usb4->dev)) {
+		ret = component_add(&usb4->dev, &connector_ops);
+		if (ret) {
+			dev_err(&usb4->dev, "failed to add component\n");
+			device_unregister(&usb4->dev);
+		}
+	}
+
 	pm_runtime_no_callbacks(&usb4->dev);
 	pm_runtime_set_active(&usb4->dev);
 	pm_runtime_enable(&usb4->dev);
@@ -265,6 +301,8 @@ struct usb4_port *usb4_port_device_add(struct tb_port *port)
  */
 void usb4_port_device_remove(struct usb4_port *usb4)
 {
+	if (dev_fwnode(&usb4->dev))
+		component_del(&usb4->dev, &connector_ops);
 	device_unregister(&usb4->dev);
 }