usb: roles: Link the switch to its connector

This is probable useful information to have in user space in
general, but it's primarily needed for the xHCI DbC (Debug
Capability). When xHCI DbC is being used, the USB port needs
to be muxed to the xHCI even in device role. In xHCI DbC mode,
the xHCI is the USB device controller.
Tested-by: Uday Bhat <uday.m.bhat@intel.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20240213130018.3029991-2-heikki.krogerus@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-class-usb_role

@@ -19,3 +19,9 @@ Description:
 		- none
 		- host
 		- device
+
+What:		/sys/class/usb_role/<switch>/connector
+Date:		Feb 2024
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		Optional symlink to the USB Type-C connector.

drivers/usb/roles/class.c

@@ -7,6 +7,7 @@
  *         Hans de Goede <hdegoede@redhat.com>
  */
 
+#include <linux/component.h>
 #include <linux/usb/role.h>
 #include <linux/property.h>
 #include <linux/device.h>
@@ -34,6 +35,32 @@ struct usb_role_switch {
 
 #define to_role_switch(d)	container_of(d, struct usb_role_switch, dev)
 
+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, "usb-role-switch");
+	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, "usb-role-switch");
+	sysfs_remove_link(&dev->kobj, "connector");
+}
+
+static const struct component_ops connector_ops = {
+	.bind = connector_bind,
+	.unbind = connector_unbind,
+};
+
 /**
  * usb_role_switch_set_role - Set USB role for a switch
  * @sw: USB role switch
@@ -352,6 +379,12 @@ usb_role_switch_register(struct device *parent,
 		return ERR_PTR(ret);
 	}
 
+	if (dev_fwnode(&sw->dev)) {
+		ret = component_add(&sw->dev, &connector_ops);
+		if (ret)
+			dev_warn(&sw->dev, "failed to add component\n");
+	}
+
 	/* TODO: Symlinks for the host port and the device controller. */
 
 	return sw;
@@ -366,8 +399,11 @@ EXPORT_SYMBOL_GPL(usb_role_switch_register);
  */
 void usb_role_switch_unregister(struct usb_role_switch *sw)
 {
-	if (!IS_ERR_OR_NULL(sw))
-		device_unregister(&sw->dev);
+	if (IS_ERR_OR_NULL(sw))
+		return;
+	if (dev_fwnode(&sw->dev))
+		component_del(&sw->dev, &connector_ops);
+	device_unregister(&sw->dev);
 }
 EXPORT_SYMBOL_GPL(usb_role_switch_unregister);