usb-serial: new API for driver registration

This patch (as1522) adds two new routines to the usb-serial core, for
registering and unregistering serial drivers.  Instead of registering
the usb_driver and usb_serial_drivers separately, with error checking
for each one, the drivers can all be registered and unregistered by a
single function call.  This reduces duplicated code.

More importantly, the new core routines change the order in which the
drivers are registered.  Currently the usb-serial drivers are all
registered first and the usb_driver is done last, which leaves a
window for problems.  A udev script may quickly add a new dynamic-ID
for a usb-serial driver, causing the corresponding usb_driver to be
probed.  If the usb_driver hasn't been registered yet then an oops
will occur.

The new routine prevents such problems by registering the usb_driver
first.  To insure that it gets probed properly for already-attached
serial devices, we call driver_attach() after all the usb-serial
drivers have been registered.

Along with adding the new routines, the patch modifies the "generic"
serial driver to use them.  Further patches will similarly modify all
the other in-tree USB serial drivers.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/generic.c

@@ -54,7 +54,6 @@ static struct usb_driver generic_driver = {
 	.probe =	generic_probe,
 	.disconnect =	usb_serial_disconnect,
 	.id_table =	generic_serial_ids,
-	.no_dynamic_id =	1,
 };
 
 /* All of the device info needed for the Generic Serial Converter */
@@ -64,7 +63,6 @@ struct usb_serial_driver usb_serial_generic_device = {
 		.name =		"generic",
 	},
 	.id_table =		generic_device_ids,
-	.usb_driver = 		&generic_driver,
 	.num_ports =		1,
 	.disconnect =		usb_serial_generic_disconnect,
 	.release =		usb_serial_generic_release,
@@ -73,6 +71,10 @@ struct usb_serial_driver usb_serial_generic_device = {
 	.resume =		usb_serial_generic_resume,
 };
 
+static struct usb_serial_driver * const serial_drivers[] = {
+	&usb_serial_generic_device, NULL
+};
+
 static int generic_probe(struct usb_interface *interface,
 			       const struct usb_device_id *id)
 {
@@ -97,13 +99,7 @@ int usb_serial_generic_register(int _debug)
 		USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;
 
 	/* register our generic driver with ourselves */
-	retval = usb_serial_register(&usb_serial_generic_device);
-	if (retval)
-		goto exit;
-	retval = usb_register(&generic_driver);
-	if (retval)
-		usb_serial_deregister(&usb_serial_generic_device);
-exit:
+	retval = usb_serial_register_drivers(&generic_driver, serial_drivers);
 #endif
 	return retval;
 }
@@ -112,8 +108,7 @@ void usb_serial_generic_deregister(void)
 {
 #ifdef CONFIG_USB_SERIAL_GENERIC
 	/* remove our generic driver */
-	usb_deregister(&generic_driver);
-	usb_serial_deregister(&usb_serial_generic_device);
+	usb_serial_deregister_drivers(&generic_driver, serial_drivers);
 #endif
 }