[patch]usb_serial_driver insufficient for clean disconnect handling

Hi,

it seems to me that for several usb serial drivers it is currently
impossible to cleanly handle disconnect, because usb_serial_driver
lacks a needed method.

As we often discussed, before a disconnect handler may return, it has
to finish all IO to the device. That means that usb_kill_urb() has to be
called on all URBs that might be active.
The serial driver does kill all standard URBs (bulk/interrupt in/out)
but it does not and indeed cannot deal with any private URBs (eg.
control URBs as in mos7720/mos7840).
The shutdown() method is unable to do the job because it can be
delayed if additional references to the port exist.

To allow killing them in time I propose this additional method for
usb_serial_driver.

	Regards
		Oliver

Signed-off-by: Oliver Neukum <[email protected]>
-----

--- linux-2.6.21-rc3-git7/include/linux/usb/serial.h~	2007-03-12 19:32:27.000000000 +0100
+++ linux-2.6.21-rc3-git7/include/linux/usb/serial.h	2007-03-15 13:54:37.000000000 +0100
@@ -214,6 +214,7 @@
 
 	int (*probe) (struct usb_serial *serial, const struct usb_device_id *id);
 	int (*attach) (struct usb_serial *serial);
+	void (*detach) (struct usb_serial *serial);
 	int (*calc_num_ports) (struct usb_serial *serial);
 
 	void (*shutdown) (struct usb_serial *serial);
--- linux-2.6.21-rc3-git7/drivers/usb/serial/usb-serial.c~	2007-03-12 19:32:59.000000000 +0100
+++ linux-2.6.21-rc3-git7/drivers/usb/serial/usb-serial.c	2007-03-15 13:54:34.000000000 +0100
@@ -1064,6 +1064,10 @@
 				kill_traffic(port);
 			}
 		}
+		/* allow the subdriver to cleanly kill
+		 * private URBs */
+		if (serial->type->detach)
+			(serial->type->detach)(serial);
 		/* let the last holder of this object 
 		 * cause it to be cleaned up */
 		usb_serial_put(serial);

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