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>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index 10cb74d2ad1..8c8dbf9c5b8 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -300,8 +300,17 @@ struct usb_serial_driver {
 #define to_usb_serial_driver(d) \
         container_of(d, struct usb_serial_driver, driver)
 
+/*
+ * These two routines are kept only for backward compatibility.
+ * Don't use them; call usb_serial_{de}register_drivers() instead.
+ */
 extern int  usb_serial_register(struct usb_serial_driver *driver);
 extern void usb_serial_deregister(struct usb_serial_driver *driver);
+
+extern int usb_serial_register_drivers(struct usb_driver *udriver,
+                struct usb_serial_driver * const serial_drivers[]);
+extern void usb_serial_deregister_drivers(struct usb_driver *udriver,
+                struct usb_serial_driver * const serial_drivers[]);
 extern void usb_serial_port_softint(struct usb_serial_port *port);
 
 extern int usb_serial_probe(struct usb_interface *iface,