From 8ca1932fef3d39a25af69d126f3d8897f1014167 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Mon, 21 Aug 2006 12:08:19 -0400
Subject: [PATCH] --- yaml --- r: 36431 b: refs/heads/master c:
 088dc270e1da03744d977cbd9edd4311af142348 h: refs/heads/master i:   36429:
 daacbbabad935fd1804e697796bb2f05954bad4f   36427:
 11d5a900e624466224966463e032ce25d85a1a81   36423:
 70a92e42329d6fd03b4d3939f57c9e9c6cc5d375   36415:
 5ab9b0cbd779b2b679e3ad902bab985b74badfda v: v3

---
 [refs]                           |  2 +-
 trunk/drivers/usb/core/message.c | 59 ++++++++++++++++++++++++++++++++
 trunk/include/linux/usb.h        |  3 ++
 3 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 95abd2bb066c..adccbaaa2299 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3a3416b12f1fbd607bc137a57c924a628aa5485c
+refs/heads/master: 088dc270e1da03744d977cbd9edd4311af142348
diff --git a/trunk/drivers/usb/core/message.c b/trunk/drivers/usb/core/message.c
index 49cfd7928a1c..333b22c68aa4 100644
--- a/trunk/drivers/usb/core/message.c
+++ b/trunk/drivers/usb/core/message.c
@@ -1493,6 +1493,65 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
 	return 0;
 }
 
+struct set_config_request {
+	struct usb_device	*udev;
+	int			config;
+	struct work_struct	work;
+};
+
+/* Worker routine for usb_driver_set_configuration() */
+static void driver_set_config_work(void *_req)
+{
+	struct set_config_request *req = _req;
+
+	usb_lock_device(req->udev);
+	usb_set_configuration(req->udev, req->config);
+	usb_unlock_device(req->udev);
+	usb_put_dev(req->udev);
+	kfree(req);
+}
+
+/**
+ * usb_driver_set_configuration - Provide a way for drivers to change device configurations
+ * @udev: the device whose configuration is being updated
+ * @config: the configuration being chosen.
+ * Context: In process context, must be able to sleep
+ *
+ * Device interface drivers are not allowed to change device configurations.
+ * This is because changing configurations will destroy the interface the
+ * driver is bound to and create new ones; it would be like a floppy-disk
+ * driver telling the computer to replace the floppy-disk drive with a
+ * tape drive!
+ *
+ * Still, in certain specialized circumstances the need may arise.  This
+ * routine gets around the normal restrictions by using a work thread to
+ * submit the change-config request.
+ *
+ * Returns 0 if the request was succesfully queued, error code otherwise.
+ * The caller has no way to know whether the queued request will eventually
+ * succeed.
+ */
+int usb_driver_set_configuration(struct usb_device *udev, int config)
+{
+	struct set_config_request *req;
+
+	req = kmalloc(sizeof(*req), GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+	req->udev = udev;
+	req->config = config;
+	INIT_WORK(&req->work, driver_set_config_work, req);
+
+	usb_get_dev(udev);
+	if (!schedule_work(&req->work)) {
+		usb_put_dev(udev);
+		kfree(req);
+		return -EINVAL;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_driver_set_configuration);
+
 // synchronous request completion model
 EXPORT_SYMBOL(usb_control_msg);
 EXPORT_SYMBOL(usb_bulk_msg);
diff --git a/trunk/include/linux/usb.h b/trunk/include/linux/usb.h
index 26d8a5f36896..f104efa04d79 100644
--- a/trunk/include/linux/usb.h
+++ b/trunk/include/linux/usb.h
@@ -1099,6 +1099,9 @@ extern int usb_clear_halt(struct usb_device *dev, int pipe);
 extern int usb_reset_configuration(struct usb_device *dev);
 extern int usb_set_interface(struct usb_device *dev, int ifnum, int alternate);
 
+/* this request isn't really synchronous, but it belongs with the others */
+extern int usb_driver_set_configuration(struct usb_device *udev, int config);
+
 /*
  * timeouts, in milliseconds, used for sending/receiving control messages
  * they typically complete within a few frames (msec) after they're issued