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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〉.