USB: core: Add API to change the wireless_status

This adds the API that allows device specific drivers to tell user-space
about whether the wireless device is connected to its receiver dongle.

See "USB: core: Add wireless_status sysfs attribute" for a detailed
explanation of what this attribute should be used for.
Signed-off-by: Bastien Nocera <hadess@hadess.net>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20230302105555.51417-5-hadess@hadess.netSigned-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/usb/core/message.c

@@ -1908,6 +1908,45 @@ static void __usb_queue_reset_device(struct work_struct *ws)
 	usb_put_intf(iface);	/* Undo _get_ in usb_queue_reset_device() */
 }
 
+/*
+ * Internal function to set the wireless_status sysfs attribute
+ * See usb_set_wireless_status() for more details
+ */
+static void __usb_wireless_status_intf(struct work_struct *ws)
+{
+	struct usb_interface *iface =
+		container_of(ws, struct usb_interface, wireless_status_work);
+
+	device_lock(iface->dev.parent);
+	if (iface->sysfs_files_created)
+		usb_update_wireless_status_attr(iface);
+	device_unlock(iface->dev.parent);
+	usb_put_intf(iface);	/* Undo _get_ in usb_set_wireless_status() */
+}
+
+/**
+ * usb_set_wireless_status - sets the wireless_status struct member
+ * @dev: the device to modify
+ * @status: the new wireless status
+ *
+ * Set the wireless_status struct member to the new value, and emit
+ * sysfs changes as necessary.
+ *
+ * Returns: 0 on success, -EALREADY if already set.
+ */
+int usb_set_wireless_status(struct usb_interface *iface,
+		enum usb_wireless_status status)
+{
+	if (iface->wireless_status == status)
+		return -EALREADY;
+
+	usb_get_intf(iface);
+	iface->wireless_status = status;
+	schedule_work(&iface->wireless_status_work);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_set_wireless_status);
 
 /*
  * usb_set_configuration - Makes a particular device setting be current
@@ -2100,6 +2139,7 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
 		intf->dev.type = &usb_if_device_type;
 		intf->dev.groups = usb_interface_groups;
 		INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
+		INIT_WORK(&intf->wireless_status_work, __usb_wireless_status_intf);
 		intf->minor = -1;
 		device_initialize(&intf->dev);
 		pm_runtime_no_callbacks(&intf->dev);

include/linux/usb.h

@@ -262,6 +262,7 @@ struct usb_interface {
 	unsigned resetting_device:1;	/* true: bandwidth alloc after reset */
 	unsigned authorized:1;		/* used for interface authorization */
 	enum usb_wireless_status wireless_status;
+	struct work_struct wireless_status_work;
 
 	struct device dev;		/* interface specific device info */
 	struct device *usb_dev;
@@ -896,6 +897,10 @@ static inline int usb_interface_claimed(struct usb_interface *iface)
 
 extern void usb_driver_release_interface(struct usb_driver *driver,
 			struct usb_interface *iface);
+
+int usb_set_wireless_status(struct usb_interface *iface,
+			enum usb_wireless_status status);
+
 const struct usb_device_id *usb_match_id(struct usb_interface *interface,
 					 const struct usb_device_id *id);
 extern int usb_match_one_id(struct usb_interface *interface,