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DEVICE_IDENTIFY(9)	    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	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 ker-
     nel  by  calling bus_set_resource() for each resource (refer to bus_set_re-
     source(9) for more information).

     Since the device tree and the device driver  tree	are  disjoint,	the  DE-
     VICE_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  mea-
     sure 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), DE-
     VICE_ATTACH(9), DEVICE_DETACH(9), DEVICE_PROBE(9), DEVICE_SHUTDOWN(9)

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

FreeBSD 13.5			January 15, 2017	      DEVICE_IDENTIFY(9)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=DEVICE_IDENTIFY&sektion=9&manpath=FreeBSD+13.5-RELEASE+and+Ports>

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