bus_child_present (9)

Leading comments

Copyright (c) 2003 M. Warner Losh

All rights reserved.

This program is free software.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer...

(The comments found at the beginning of the groff file "man9/bus_child_present.9freebsd".)

NAME

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

SYNOPSIS

In sys/param.h In sys/bus.h

In machine/bus.h In sys/rman.h In machine/resource.h Ft int Fn bus_child_present device_t dev

DESCRIPTION

The Fn bus_child_present function requests that the parent device driver of Fa dev check to see if the hardware represented by Fa 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 Fn 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_children9.

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 An Warner Losh Aq imp@FreeBSD.org .