xref: /freebsd/share/man/man9/bus_child_present.9 (revision 4b9d6057)
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25.Dd March 27, 2003
26.Dt BUS_CHILD_PRESENT 9
27.Os
28.Sh NAME
29.Nm bus_child_present
30.Nd "ask the bus driver to see if this device is still really present"
31.Sh SYNOPSIS
32.In sys/param.h
33.In sys/bus.h
34.Pp
35.In machine/bus.h
36.In sys/rman.h
37.In machine/resource.h
38.Ft int
39.Fn bus_child_present "device_t dev"
40.Sh DESCRIPTION
41The
42.Fn bus_child_present
43function requests that the parent device driver of
44.Fa dev
45check to see if the
46hardware represented by
47.Fa dev
48is still physically accessible at this time.
49While the notion of accessible varies from bus to bus, generally
50hardware that is not accessible cannot be accessed via the
51.Fn bus_space*
52methods that would otherwise be used to access the device.
53.Pp
54This does not ask the question
55.Dq does this device have children?
56which can better be answered by
57.Xr device_get_children 9 .
58.Sh RETURN VALUES
59A zero return value indicates that the device is not present in the
60system.
61A non-zero return value indicates that the device is present in the
62system, or that the state of the device cannot be determined.
63.Sh EXAMPLES
64This is some example code.
65It only calls stop when the
66.Xr dc 4
67device is actually present.
68.Bd -literal -offset indent
69device_t dev;
70dc_softc *sc;
71
72sc = device_get_softc(dev);
73if (bus_child_present(dev))
74	dc_stop(sc);
75.Ed
76.Sh SEE ALSO
77.Xr device 9 ,
78.Xr driver 9
79.Sh AUTHORS
80This manual page was written by
81.An Warner Losh Aq Mt imp@FreeBSD.org .
82