driver model: allow manual binding of devices to drivers.

This creates and exports device_bind_driver() and device_release_driver()
that allow a caller to manually bind a device to a driver. Apparantly, some
drivers use this functionality (like USB): a driver binds to other device
interfaces during the driver's probe() method call for the first interface.

Implementation is easy enough, since it simply involves renaming and exporting
the internal functions attach() and detach().

drivers/base/bus.c

@@ -224,13 +224,19 @@ int bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
 }
 
 /**
- *	attach - add device to driver.
+ *	device_bind_driver - bind a driver to one device.
  *	@dev:	device.
  *
- *	By this point, we know for sure what the driver is, so we 
- *	do the rest (which ain't that much).
+ *	Allow manual attachment of a driver to a deivce.
+ *	Caller must have already set @dev->driver.
+ *
+ *	Note that this does not modify the bus reference count 
+ *	nor take the bus's rwsem. Please verify those are accounted 
+ *	for before calling this. (It is ok to call with no other effort
+ *	from a driver's probe() method.)
  */
-static void attach(struct device * dev)
+
+void device_bind_driver(struct device * dev)
 {
 	pr_debug("bound device '%s' to driver '%s'\n",
 		 dev->bus_id,dev->driver->name);
@@ -259,15 +265,14 @@ static int bus_match(struct device * dev, struct device_driver * drv)
 	if (dev->bus->match(dev,drv)) {
 		dev->driver = drv;
 		if (drv->probe) {
-			if (!(error = drv->probe(dev)))
-				attach(dev);
-			else 
+			if ((error = drv->probe(dev))) {
 				dev->driver = NULL;
-		} else {
-			attach(dev);
-			error = 0;
+				return error;
 			}
 		}
+		device_bind_driver(dev);
+		error = 0;
+	}
 	return error;
 }
 
@@ -286,7 +291,7 @@ static int device_attach(struct device * dev)
 	int error = 0;
 
 	if (dev->driver) {
-		attach(dev);
+		device_bind_driver(dev);
 		return 0;
 	}
 
@@ -333,16 +338,18 @@ static int driver_attach(struct device_driver * drv)
 
 
 /**
- *	detach - do dirty work of detaching device from its driver.
+ *	device_release_driver - manually detach device from driver.
  *	@dev:	device.
- *	@drv:	its driver.
  *
- *	Note that calls to this function are serialized by taking the 
- *	bus's rwsem in both bus_remove_device() and bus_remove_driver().
+ *	Manually detach device from driver.
+ *	Note that this is called without incrementing the bus
+ *	reference count nor taking the bus's rwsem. Be sure that
+ *	those are accounted for before calling this function.
  */
 
-static void detach(struct device * dev, struct device_driver * drv)
+void device_release_driver(struct device * dev)
 {
+	struct device_driver * drv = dev->driver;
 	if (drv) {
 		sysfs_remove_link(&drv->kobj,dev->kobj.name);
 		list_del_init(&dev->driver_list);
@@ -354,17 +361,6 @@ static void detach(struct device * dev, struct device_driver * drv)
 }
 
 
-/**
- *	device_detach - detach device from its driver.
- *	@dev:	device.
- */
-
-static void device_detach(struct device * dev)
-{
-	detach(dev,dev->driver);
-}
-
-
 /**
  *	driver_detach - detach driver from all devices it controls.
  *	@drv:	driver.
@@ -375,7 +371,7 @@ static void driver_detach(struct device_driver * drv)
 	struct list_head * entry, * next;
 	list_for_each_safe(entry,next,&drv->devices) {
 		struct device * dev = container_of(entry,struct device,driver_list);
-		detach(dev,drv);
+		device_release_driver(dev);
 	}
 	
 }
@@ -417,7 +413,7 @@ void bus_remove_device(struct device * dev)
 		sysfs_remove_link(&dev->bus->devices.kobj,dev->bus_id);
 		down_write(&dev->bus->subsys.rwsem);
 		pr_debug("bus %s: remove device %s\n",dev->bus->name,dev->bus_id);
-		device_detach(dev);
+		device_release_driver(dev);
 		list_del_init(&dev->bus_list);
 		up_write(&dev->bus->subsys.rwsem);
 		put_bus(dev->bus);
@@ -534,6 +530,9 @@ core_initcall(bus_subsys_init);
 EXPORT_SYMBOL(bus_for_each_dev);
 EXPORT_SYMBOL(bus_for_each_drv);
 
+EXPORT_SYMBOL(device_bind_driver);
+EXPORT_SYMBOL(device_release_driver);
+
 EXPORT_SYMBOL(bus_add_device);
 EXPORT_SYMBOL(bus_remove_device);
 EXPORT_SYMBOL(bus_register);

include/linux/device.h

@@ -306,6 +306,14 @@ extern void device_initialize(struct device * dev);
 extern int device_add(struct device * dev);
 extern void device_del(struct device * dev);
 
+/*
+ * Manual binding of a device to driver. See drivers/base/bus.c 
+ * for information on use.
+ */
+extern void device_bind_driver(struct device * dev);
+extern void device_release_driver(struct device * dev);
+
+
 /* driverfs interface for exporting device attributes */
 
 struct device_attribute {