centos man page for device_add

DEVICE_ADD(9)						   Device drivers infrastructure					     DEVICE_ADD(9)

NAME
       device_add - add device to device hierarchy.

SYNOPSIS
       int device_add(struct device * dev);

ARGUMENTS
       dev
	   device.

DESCRIPTION
       This is part 2 of device_register, though may be called separately _iff_ device_initialize has been called separately.

       This adds dev to the kobject hierarchy via kobject_add, adds it to the global and sibling lists for the device, then adds it to the other
       relevant subsystems of the driver model.

       Do not call this routine or device_register more than once for any device structure. The driver model core is not designed to work with
       devices that get unregistered and then spring back to life. (Among other things, it's very hard to guarantee that all references to the
       previous incarnation of dev have been dropped.) Allocate and register a fresh new struct device instead.

NOTE
       _Never_ directly free dev after calling this function, even if it returned an error! Always use put_device to give up your reference
       instead.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							     DEVICE_ADD(9)