Add documentation on meaning of -EPROBE_DEFER

See the kerneldoc for the struct device_driver.

Allocation

~~~~~~~~~~

A driver's probe() may return a negative errno value to indicate that

the driver did not bind to this device, in which case it should have

released all resources it allocated::

released all resources it allocated.

Optionally, probe() may return -EPROBE_DEFER if the driver depends on

resources that are not yet available (e.g., supplied by a driver that

hasn't initialized yet).  The driver core will put the device onto the

deferred probe list and will try to call it again later. If a driver

must defer, it should return -EPROBE_DEFER as early as possible to

reduce the amount of time spent on setup work that will need to be

unwound and reexecuted at a later time.

.. warning::

      -EPROBE_DEFER must not be returned if probe() has already created

      child devices, even if those child devices are removed again

      in a cleanup path. If -EPROBE_DEFER is returned after a child

      device has been registered, it may result in an infinite loop of

      .probe() calls to the same driver.

::

	void	(*sync_state)	(struct device *dev);

not restricted to that. Use it whenever it makes sense to take an action after

all the consumers of a device have probed::

::

	int 	(*remove)	(struct device *dev);

remove is called to unbind a driver from a device. This may be

device; i.e. anything in the device's driver_data field.

If the device is still present, it should quiesce the device and place

it into a supported low-power state::

it into a supported low-power state.

::

	int	(*suspend)	(struct device *dev, pm_message_t state);

suspend is called to put the device in a low power state::

suspend is called to put the device in a low power state.

::

	int	(*resume)	(struct device *dev);