NAME

       bus_child_present — ask the bus driver to see if this device is still really present

SYNOPSIS

       #include <sys/param.h>
       #include <sys/bus.h>

       #include <machine/bus.h>
       #include <sys/rman.h>
       #include <machine/resource.h>

       int
       bus_child_present(device_t dev);

DESCRIPTION

       The  bus_child_present()  function  requests  that  the  parent  device driver of dev check to see if the
       hardware represented by dev is still physically accessible at this time.  While the notion of  accessible
       varies from bus to bus, generally hardware that is not accessible cannot be accessed via the bus_space*()
       methods that would otherwise be used to access the device.

       This  does  not  ask  the  question  “does  this  device  have children?” which can better be answered by
       device_get_children(9).

RETURN VALUES

       A zero return value indicates that the device is not present in the  system.   A  non-zero  return  value
       indicates that the device is present in the system, or that the state of the device cannot be determined.

EXAMPLES

       This is some example code.  It only calls stop when the dc(4) device is actually present.

             device_t dev;
             dc_softc *sc;

             sc = device_get_softc(dev);
             if (bus_child_present(dev))
                     dc_stop(sc);

SEE ALSO

       device(9), driver(9)

AUTHORS

       This manual page was written by Warner Losh <imp@FreeBSD.org>.

Debian                                           March 27, 2003                             BUS_CHILD_PRESENT(9)