freebsd man page for device_identify

DEVICE_IDENTIFY(9)					   BSD Kernel Developer's Manual					DEVICE_IDENTIFY(9)

NAME
     DEVICE_IDENTIFY -- identify a device, register it

SYNOPSIS
     #include <sys/param.h>
     #include <sys/bus.h>

     void
     DEVICE_IDENTIFY(driver_t *driver, device_t parent);

DESCRIPTION
     The identify function for a device is only needed for devices on busses that cannot identify their children independently, e.g. the ISA bus.
     It is used to recognize the device (usually done by accessing non-ambiguous registers in the hardware) and to tell the kernel about it and
     thus creating a new device instance.

     BUS_ADD_CHILD(9) is used to register the device as a child of the bus.  The device's resources (such as IRQ and I/O ports) are registered
     with the kernel by calling bus_set_resource() for each resource (refer to bus_set_resource(9) for more information).

     Since the device tree and the device driver tree are disjoint, the DEVICE_IDENTIFY() routine needs to take this into account.  If you load
     and unload your device driver that has the identify routine, the child node has the potential for adding the same node multiple times unless
     specific measure are taken to preclude that possibility.

EXAMPLES
     The following pseudo-code shows an example of a function that probes for a piece of hardware and registers it and its resource (an I/O port)
     with the kernel.

     void
     foo_identify(driver_t *driver, device_t parent)
     {
	     device_t child;

	     retrieve_device_information;
	     if (devices matches one of your supported devices &&
		 not already in device tree) {
		     child = BUS_ADD_CHILD(parent, 0, "foo", -1);
		     bus_set_resource(child, SYS_RES_IOPORT, 0, FOO_IOADDR, 1);
	     }
     }

SEE ALSO
     BUS_ADD_CHILD(9), bus_set_resource(9), device(9), device_add_child(9), DEVICE_ATTACH(9), DEVICE_DETACH(9), DEVICE_PROBE(9),
     DEVICE_SHUTDOWN(9)

AUTHORS
     This manual page was written by Alexander Langer <alex@FreeBSD.org>.

BSD
								   May 13, 2004 							       BSD