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 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>.