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>.