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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〉.