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⟩.