[PATCH] usbcore: port reset for composite devices

This patch (as699) adds usb_reset_composite_device(), a routine for
sending a USB port reset to a device with multiple interfaces owned by
different drivers.  Drivers are notified about impending and completed
resets through two new methods in the usb_driver structure.

The patch modifieds the usbfs ioctl code to make it use the new routine
instead of usb_reset_device().  Follow-up patches will modify the hub,
usb-storage, and usbhid drivers so they can utilize this new API.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/devio.c

@@ -823,8 +823,7 @@ static int proc_connectinfo(struct dev_state *ps, void __user *arg)
 
 static int proc_resetdevice(struct dev_state *ps)
 {
-	return usb_reset_device(ps->dev);
-
+	return usb_reset_composite_device(ps->dev, NULL);
 }
 
 static int proc_setintf(struct dev_state *ps, void __user *arg)

drivers/usb/core/hub.c

@@ -3007,9 +3007,9 @@ static int config_descriptors_changed(struct usb_device *udev)
  * usb_reset_device - perform a USB port reset to reinitialize a device
  * @udev: device to reset (not in SUSPENDED or NOTATTACHED state)
  *
- * WARNING - don't reset any device unless drivers for all of its
- * interfaces are expecting that reset!  Maybe some driver->reset()
- * method should eventually help ensure sufficient cooperation.
+ * WARNING - don't use this routine to reset a composite device
+ * (one with multiple interfaces owned by separate drivers)!
+ * Use usb_reset_composite_device() instead.
  *
  * Do a port reset, reassign the device's address, and establish its
  * former operating configuration.  If the reset fails, or the device's
@@ -3125,3 +3125,81 @@ int usb_reset_device(struct usb_device *udev)
 	hub_port_logical_disconnect(parent_hub, port1);
 	return -ENODEV;
 }
+
+/**
+ * usb_reset_composite_device - warn interface drivers and perform a USB port reset
+ * @udev: device to reset (not in SUSPENDED or NOTATTACHED state)
+ * @iface: interface bound to the driver making the request (optional)
+ *
+ * Warns all drivers bound to registered interfaces (using their pre_reset
+ * method), performs the port reset, and then lets the drivers know that
+ * the reset is over (using their post_reset method).
+ *
+ * Return value is the same as for usb_reset_device().
+ *
+ * The caller must own the device lock.  For example, it's safe to use
+ * this from a driver probe() routine after downloading new firmware.
+ * For calls that might not occur during probe(), drivers should lock
+ * the device using usb_lock_device_for_reset().
+ *
+ * The interface locks are acquired during the pre_reset stage and released
+ * during the post_reset stage.  However if iface is not NULL and is
+ * currently being probed, we assume that the caller already owns its
+ * lock.
+ */
+int usb_reset_composite_device(struct usb_device *udev,
+		struct usb_interface *iface)
+{
+	int ret;
+	struct usb_host_config *config = udev->actconfig;
+
+	if (udev->state == USB_STATE_NOTATTACHED ||
+			udev->state == USB_STATE_SUSPENDED) {
+		dev_dbg(&udev->dev, "device reset not allowed in state %d\n",
+				udev->state);
+		return -EINVAL;
+	}
+
+	if (iface && iface->condition != USB_INTERFACE_BINDING)
+		iface = NULL;
+
+	if (config) {
+		int i;
+		struct usb_interface *cintf;
+		struct usb_driver *drv;
+
+		for (i = 0; i < config->desc.bNumInterfaces; ++i) {
+			cintf = config->interface[i];
+			if (cintf != iface)
+				down(&cintf->dev.sem);
+			if (device_is_registered(&cintf->dev) &&
+					cintf->dev.driver) {
+				drv = to_usb_driver(cintf->dev.driver);
+				if (drv->pre_reset)
+					(drv->pre_reset)(cintf);
+			}
+		}
+	}
+
+	ret = usb_reset_device(udev);
+
+	if (config) {
+		int i;
+		struct usb_interface *cintf;
+		struct usb_driver *drv;
+
+		for (i = config->desc.bNumInterfaces - 1; i >= 0; --i) {
+			cintf = config->interface[i];
+			if (device_is_registered(&cintf->dev) &&
+					cintf->dev.driver) {
+				drv = to_usb_driver(cintf->dev.driver);
+				if (drv->post_reset)
+					(drv->post_reset)(cintf);
+			}
+			if (cintf != iface)
+				up(&cintf->dev.sem);
+		}
+	}
+
+	return ret;
+}

drivers/usb/core/usb.c

@@ -1207,6 +1207,7 @@ EXPORT_SYMBOL(usb_ifnum_to_if);
 EXPORT_SYMBOL(usb_altnum_to_altsetting);
 
 EXPORT_SYMBOL(usb_reset_device);
+EXPORT_SYMBOL(usb_reset_composite_device);
 
 EXPORT_SYMBOL(__usb_get_extra_descriptor);
 

include/linux/usb.h

@@ -386,6 +386,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev,
 
 /* USB port reset for device reinitialization */
 extern int usb_reset_device(struct usb_device *dev);
+extern int usb_reset_composite_device(struct usb_device *dev,
+		struct usb_interface *iface);
 
 extern struct usb_device *usb_find_device(u16 vendor_id, u16 product_id);
 
@@ -554,6 +556,10 @@ struct usb_dynids {
  *	do (or don't) show up otherwise in the filesystem.
  * @suspend: Called when the device is going to be suspended by the system.
  * @resume: Called when the device is being resumed by the system.
+ * @pre_reset: Called by usb_reset_composite_device() when the device
+ *	is about to be reset.
+ * @post_reset: Called by usb_reset_composite_device() after the device
+ *	has been reset.
  * @id_table: USB drivers use ID table to support hotplugging.
  *	Export this with MODULE_DEVICE_TABLE(usb,...).  This must be set
  *	or your driver's probe function will never get called.
@@ -592,6 +598,9 @@ struct usb_driver {
 	int (*suspend) (struct usb_interface *intf, pm_message_t message);
 	int (*resume) (struct usb_interface *intf);
 
+	void (*pre_reset) (struct usb_interface *intf);
+	void (*post_reset) (struct usb_interface *intf);
+
 	const struct usb_device_id *id_table;
 
 	struct usb_dynids dynids;