xref: /freebsd/share/man/man9/bus_child_present.9 (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
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29.\" $FreeBSD$
30.\"
31.Dd March 27, 2003
32.Dt BUS_CHILD_PRESENT 9
33.Os
34.Sh NAME
35.Nm bus_child_present
36.Nd "ask the bus driver to see if this device is still really present"
37.Sh SYNOPSIS
38.In sys/param.h
39.In sys/bus.h
40.Pp
41.In machine/bus.h
42.In sys/rman.h
43.In machine/resource.h
44.Ft int
45.Fn bus_child_present "device_t dev"
46.Sh DESCRIPTION
47The
48.Fn bus_child_present
49function requests that the parent device driver of
50.Fa dev
51check to see if the
52hardware represented by
53.Fa dev
54is still physically accessible at this time.
55While the notion of accessible varies from bus to bus, generally
56hardware that is not accessible cannot be accessed via the
57.Fn bus_space*
58methods that would otherwise be used to access the device.
59.Pp
60This does not ask the question
61.Dq does this device have children?
62which can better be answered by
63.Xr device_get_children 9 .
64.Sh RETURN VALUES
65A zero return value indicates that the device is not present in the
66system.
67A non-zero return value indicates that the device is present in the
68system, or that the state of the device cannot be determined.
69.Sh EXAMPLES
70This is some example code.
71It only calls stop when the
72.Xr dc 4
73device is actually present.
74.Bd -literal -offset indent
75device_t dev;
76dc_softc *sc;
77
78sc = device_get_softc(dev);
79if (bus_child_present(dev))
80	dc_stop(sc);
81.Ed
82.Sh SEE ALSO
83.Xr device 9 ,
84.Xr driver 9
85.Sh AUTHORS
86This manual page was written by
87.An Warner Losh Aq imp@FreeBSD.org .
88