driver core: emit uevents when device is bound to a driver

There are certain touch controllers that may come up in either normal
(application) or boot mode, depending on whether firmware/configuration is
corrupted when they are powered on. In boot mode the kernel does not create
input device instance (because it does not necessarily know the
characteristics of the input device in question).

Another number of controllers does not store firmware in a non-volatile
memory, and they similarly need to have firmware loaded before input device
instance is created. There are also other types of devices with similar
behavior.

There is a desire to be able to trigger firmware loading via udev, but it
has to happen only when driver is bound to a physical device (i2c or spi).
These udev actions can not use ADD events, as those happen too early, so we
are introducing BIND and UNBIND events that are emitted at the right
moment.

Also, many drivers create additional driver-specific device attributes
when binding to the device, to provide userspace with additional controls.
The new events allow userspace to adjust these driver-specific attributes
without worrying that they are not there yet.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/dd.c

@@ -259,6 +259,8 @@ static void driver_bound(struct device *dev)
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_BOUND_DRIVER, dev);
+
+	kobject_uevent(&dev->kobj, KOBJ_BIND);
 }
 
 static int driver_sysfs_add(struct device *dev)
@@ -848,6 +850,8 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 						     BUS_NOTIFY_UNBOUND_DRIVER,
 						     dev);
+
+		kobject_uevent(&dev->kobj, KOBJ_UNBIND);
 	}
 }
 

include/linux/kobject.h

@@ -57,6 +57,8 @@ enum kobject_action {
 	KOBJ_MOVE,
 	KOBJ_ONLINE,
 	KOBJ_OFFLINE,
+	KOBJ_BIND,
+	KOBJ_UNBIND,
 	KOBJ_MAX
 };
 

lib/kobject_uevent.c

@@ -50,6 +50,8 @@ static const char *kobject_actions[] = {
 	[KOBJ_MOVE] =		"move",
 	[KOBJ_ONLINE] =		"online",
 	[KOBJ_OFFLINE] =	"offline",
+	[KOBJ_BIND] =		"bind",
+	[KOBJ_UNBIND] =		"unbind",
 };
 
 /**