@@ -11,6 +11,8 @@ receive notifications from the kernel.  This can be used in conjunction with::
 
     * Block layer event notifications
 
+    * USB subsystem event notifications
+
 
 The notifications buffers can be enabled by:
 

@@ -315,6 +317,13 @@ Any particular buffer can be fed from multiple sources.  Sources include:
     or temporary link loss.  Watches of this type are set on the global device
     watch list.
 
+  * WATCH_TYPE_USB_NOTIFY
+
+    Notifications of this type indicate USB subsystem events, such as
+    attachment, removal, reset and I/O errors.  Separate events are generated
+    for buses and devices.  Watchpoints of this type are set on the global
+    device watch list.
+
 
 Event Filtering
 ===============

@@ -103,3 +103,13 @@ config USB_AUTOSUSPEND_DELAY
 	  The default value Linux has always had is 2 seconds.  Change
 	  this value if you want a different delay and cannot modify
 	  the command line or module parameter.
+
+config USB_NOTIFICATIONS
+	bool "Provide USB hardware event notifications"
+	depends on USB
+	select DEVICE_NOTIFICATIONS
+	help
+	  This option provides support for getting hardware event notifications
+	  on USB devices and interfaces.  This makes use of the
+	  /dev/watch_queue misc device to handle the notification buffer.
+	  device_notify(2) is used to set/remove watches.

@@ -41,6 +41,7 @@
 #include <linux/dma-mapping.h>
 #include <asm/byteorder.h>
 #include <linux/moduleparam.h>
+#include <linux/watch_queue.h>
 
 #include "usb.h"
 

@@ -2633,13 +2634,68 @@ static void usbdev_remove(struct usb_device *udev)
 	}
 }
 
+#ifdef CONFIG_USB_NOTIFICATIONS
+static noinline void post_usb_notification(const char *devname,
+					   enum usb_notification_type subtype,
+					   u32 error)
+{
+	unsigned int gran = WATCH_LENGTH_GRANULARITY;
+	unsigned int name_len, n_len;
+	u64 id = 0; /* Might want to put a dev# here. */
+
+	struct {
+		struct usb_notification n;
+		char more_name[USB_NOTIFICATION_MAX_NAME_LEN -
+			       (sizeof(struct usb_notification) -
+				offsetof(struct usb_notification, name))];
+	} n;
+
+	name_len = strlen(devname);
+	name_len = min_t(size_t, name_len, USB_NOTIFICATION_MAX_NAME_LEN);
+	n_len = round_up(offsetof(struct usb_notification, name) + name_len,
+			 gran) / gran;
+
+	memset(&n, 0, sizeof(n));
+	memcpy(n.n.name, devname, n_len);
+
+	n.n.watch.type		= WATCH_TYPE_USB_NOTIFY;
+	n.n.watch.subtype	= subtype;
+	n.n.watch.info		= n_len;
+	n.n.error		= error;
+	n.n.name_len		= name_len;
+
+	post_device_notification(&n.n.watch, id);
+}
+
+void post_usb_device_notification(const struct usb_device *udev,
+				  enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(dev_name(&udev->dev), subtype, error);
+}
+
+void post_usb_bus_notification(const struct usb_bus *ubus,
+			       enum usb_notification_type subtype, u32 error)
+{
+	post_usb_notification(ubus->bus_name, subtype, error);
+}
+#endif
+
 static int usbdev_notify(struct notifier_block *self,
 			       unsigned long action, void *dev)
 {
 	switch (action) {
 	case USB_DEVICE_ADD:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_ADD, 0);
 		break;
 	case USB_DEVICE_REMOVE:
+		post_usb_device_notification(dev, NOTIFY_USB_DEVICE_REMOVE, 0);
+		usbdev_remove(dev);
+		break;
+	case USB_BUS_ADD:
+		post_usb_bus_notification(dev, NOTIFY_USB_BUS_ADD, 0);
+		break;
+	case USB_BUS_REMOVE:
+		post_usb_bus_notification(dev, NOTIFY_USB_BUS_REMOVE, 0);
 		usbdev_remove(dev);
 		break;
 	}

@@ -4596,6 +4596,9 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
 				(udev->config) ? "reset" : "new", speed,
 				devnum, driver_name);
 
+	if (udev->config)
+		post_usb_device_notification(udev, NOTIFY_USB_DEVICE_RESET, 0);
+
 	/* Set up TT records, if needed  */
 	if (hdev->tt) {
 		udev->tt = hdev->tt;

@@ -2008,6 +2008,25 @@ extern void usb_led_activity(enum usb_led_event ev);
 static inline void usb_led_activity(enum usb_led_event ev) {}
 #endif
 
+/*
+ * Notification functions.
+ */
+#ifdef CONFIG_USB_NOTIFICATIONS
+extern void post_usb_device_notification(const struct usb_device *udev,
+					 enum usb_notification_type subtype,
+					 u32 error);
+extern void post_usb_bus_notification(const struct usb_bus *ubus,
+				      enum usb_notification_type subtype,
+				      u32 error);
+#else
+static inline void post_usb_device_notification(const struct usb_device *udev,
+						enum usb_notification_type subtype,
+						u32 error) {}
+static inline void post_usb_bus_notification(const struct usb_bus *ubus,
+					     enum usb_notification_type subtype,
+					     u32 error) {}
+#endif
+
 #endif  /* __KERNEL__ */
 
 #endif

@@ -12,7 +12,8 @@ enum watch_notification_type {
 	WATCH_TYPE_META		= 0,	/* Special record */
 	WATCH_TYPE_KEY_NOTIFY	= 1,	/* Key change event notification */
 	WATCH_TYPE_BLOCK_NOTIFY	= 2,	/* Block layer event notification */
-	WATCH_TYPE___NR		= 3
+	WATCH_TYPE_USB_NOTIFY	= 3,	/* USB subsystem event notification */
+	WATCH_TYPE___NR		= 4
 };
 
 enum watch_meta_notification_subtype {

@@ -139,4 +140,31 @@ struct block_notification {
 	__u64	sector;			/* Affected sector */
 };
 
+/*
+ * Type of USB layer notification.
+ */
+enum usb_notification_type {
+	NOTIFY_USB_DEVICE_ADD		= 0, /* USB device added */
+	NOTIFY_USB_DEVICE_REMOVE	= 1, /* USB device removed */
+	NOTIFY_USB_BUS_ADD		= 2, /* USB bus added */
+	NOTIFY_USB_BUS_REMOVE		= 3, /* USB bus removed */
+	NOTIFY_USB_DEVICE_RESET		= 4, /* USB device reset */
+	NOTIFY_USB_DEVICE_ERROR		= 5, /* USB device error */
+};
+
+/*
+ * USB subsystem notification record.
+ * - watch.type = WATCH_TYPE_USB_NOTIFY
+ * - watch.subtype = enum usb_notification_type
+ */
+struct usb_notification {
+	struct watch_notification watch; /* WATCH_TYPE_USB_NOTIFY */
+	__u32	error;
+	__u32	reserved;
+	__u8	name_len;		/* Length of device name */
+	__u8	name[0];		/* Device name (padded to __u64, truncated at 63 chars) */
+};
+
+#define USB_NOTIFICATION_MAX_NAME_LEN 63
+
 #endif /* _UAPI_LINUX_WATCH_QUEUE_H */