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DEVICE_IDENTIFY(9)     FreeBSD 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 buses
     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 cre-
     ating 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>.

FreeBSD	13.0		       January 15, 2017			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | AUTHORS

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