.\" Copyright (c) 2008 Konstantin Belousov
.\" All rights reserved.
.\"
.\" 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 in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/share/man/man9/dev_clone.9,v 1.2.2.1.6.1 2010/12/21 17:09:25 kensmith Exp $
.\"
.Dd January 3, 2009
.Dt DEV_CLONE 9
.Os
.Sh NAME
.Nm dev_clone ,
.Nm drain_dev_clone_events
.Nd eventhandler for name-based device cloning in devfs
.Sh SYNOPSIS
.In sys/param.h
.In sys/conf.h
.Ft void
.Fn clone_handler "void *arg" "struct ucred *cr" "char *name" "int namelen" "struct cdev **dev"
.Bd -literal
EVENTHANDLER_REGISTER(dev_clone, clone_handler, arg, priority);
.Ed
.Ft void
.Fn drain_dev_clone_events
.Sh DESCRIPTION
A device driver may register a listener that will be notified each time
a name lookup on the
.Xr devfs 5
mount point fails to find the vnode.
A listener shall be registered for the
.Va dev_clone
event.
When called, it is supplied with the first argument
.Va arg
that was specified at handler registration time,
appropriate credentials
.Va cr ,
and a name
.Va name
of length
.Va namelen
that we look for.
If the handler decides that the name is appropriate and wants to create the device
that will be associated with the name, it should return it to devfs
in the
.Va dev
argument.
.Pp
The
.Fn drain_dev_clone_events
function is a barrier.
It is guaranteed that all calls to eventhandlers for
.Nm dev_clone
that were started before
.Fn drain_dev_clone_events
call, are finished before it returns control.
.Sh SEE ALSO
.Xr devfs 5 ,
.Xr namei 9