USB: serial core should respect driver requirements

This patch (as997) fixes a bug in the USB serial core.  The core needs
to pay attention to drivers' requirements regarding the number and
type of endpoints a device has.

At the same time, the patch changes the NUM_DONT_CARE constant (which
is stored in a single-byte field) from -1 to a safer, unsigned value.
It also improves the kerneldoc for several fields in the
usb_serial_driver structure.

Finally, the patch replaces a list_for_each() with list_for_each_entry().
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -662,16 +662,14 @@ static const struct usb_device_id *get_iface_id(struct usb_serial_driver *drv,
 
 static struct usb_serial_driver *search_serial_device(struct usb_interface *iface)
 {
-	struct list_head *p;
 	const struct usb_device_id *id;
-	struct usb_serial_driver *t;
+	struct usb_serial_driver *drv;
 
 	/* Check if the usb id matches a known device */
-	list_for_each(p, &usb_serial_driver_list) {
-		t = list_entry(p, struct usb_serial_driver, driver_list);
-		id = get_iface_id(t, iface);
+	list_for_each_entry(drv, &usb_serial_driver_list, driver_list) {
+		id = get_iface_id(drv, iface);
 		if (id)
-			return t;
+			return drv;
 	}
 
 	return NULL;
@@ -811,9 +809,6 @@ int usb_serial_probe(struct usb_interface *interface,
 	/* END HORRIBLE HACK FOR PL2303 */
 #endif
 
-	/* found all that we need */
-	dev_info(&interface->dev, "%s converter detected\n", type->description);
-
 #ifdef CONFIG_USB_SERIAL_GENERIC
 	if (type == &usb_serial_generic_device) {
 		num_ports = num_bulk_out;
@@ -847,6 +842,24 @@ int usb_serial_probe(struct usb_interface *interface,
 	serial->num_interrupt_in = num_interrupt_in;
 	serial->num_interrupt_out = num_interrupt_out;
 
+	/* check that the device meets the driver's requirements */
+	if ((type->num_interrupt_in != NUM_DONT_CARE &&
+				type->num_interrupt_in != num_interrupt_in)
+			|| (type->num_interrupt_out != NUM_DONT_CARE &&
+				type->num_interrupt_out != num_interrupt_out)
+			|| (type->num_bulk_in != NUM_DONT_CARE &&
+				type->num_bulk_in != num_bulk_in)
+			|| (type->num_bulk_out != NUM_DONT_CARE &&
+				type->num_bulk_out != num_bulk_out)) {
+		dbg("wrong number of endpoints");
+		kfree(serial);
+		return -EIO;
+	}
+
+	/* found all that we need */
+	dev_info(&interface->dev, "%s converter detected\n",
+			type->description);
+
 	/* create our ports, we need as many as the max endpoints */
 	/* we don't use num_ports here cauz some devices have more endpoint pairs than ports */
 	max_endpoints = max(num_bulk_in, num_bulk_out);

include/linux/usb/serial.h

@@ -141,7 +141,7 @@ struct usb_serial {
 };
 #define to_usb_serial(d) container_of(d, struct usb_serial, kref)
 
-#define NUM_DONT_CARE	(-1)
+#define NUM_DONT_CARE	99
 
 /* get and set the serial private data pointer helper functions */
 static inline void *usb_get_serial_data (struct usb_serial *serial)
@@ -160,12 +160,18 @@ static inline void usb_set_serial_data (struct usb_serial *serial, void *data)
  *	in the syslog messages when a device is inserted or removed.
  * @id_table: pointer to a list of usb_device_id structures that define all
  *	of the devices this structure can support.
- * @num_interrupt_in: the number of interrupt in endpoints this device will
- *	have.
- * @num_interrupt_out: the number of interrupt out endpoints this device will
- *	have.
- * @num_bulk_in: the number of bulk in endpoints this device will have.
- * @num_bulk_out: the number of bulk out endpoints this device will have.
+ * @num_interrupt_in: If a device doesn't have this many interrupt-in
+ *	endpoints, it won't be sent to the driver's attach() method.
+ *	(But it might still be sent to the probe() method.)
+ * @num_interrupt_out: If a device doesn't have this many interrupt-out
+ *	endpoints, it won't be sent to the driver's attach() method.
+ *	(But it might still be sent to the probe() method.)
+ * @num_bulk_in: If a device doesn't have this many bulk-in
+ *	endpoints, it won't be sent to the driver's attach() method.
+ *	(But it might still be sent to the probe() method.)
+ * @num_bulk_out: If a device doesn't have this many bulk-out
+ *	endpoints, it won't be sent to the driver's attach() method.
+ *	(But it might still be sent to the probe() method.)
  * @num_ports: the number of different ports this device will have.
  * @calc_num_ports: pointer to a function to determine how many ports this
  *	device has dynamically.  It will be called after the probe()