OpenBSD-4.6/share/man/man9/mountroothook_establish.9

.\"	$OpenBSD: mountroothook_establish.9,v 1.2 2007/05/31 19:20:00 jmc Exp $
.\"	$NetBSD: mountroothook_establish.9,v 1.1 1995/11/25 21:24:52 perry Exp $
.\"
.\" Copyright (c) 1994 Christopher G. Demetriou
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.Dd $Mdocdate: May 31 2007 $
.Dt MOUNTROOTHOOK_ESTABLISH 9
.Os
.Sh NAME
.Nm mountroothook_establish ,
.Nm mountroothook_disestablish
.Nd add or remove a mountroot hook
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/systm.h>
.Ft void *
.Fn mountroothook_establish "void (*fn)(void *)" "void *arg"
.Ft void
.Fn mountroothook_disestablish "void *cookie"
.Sh DESCRIPTION
The
.Fn mountroothook_establish
function adds
.Fa fn
to the list of hooks invoked by
.Xr domountroothooks 9
at mountroot.
When invoked, the hook function
.Fa fn
will be passed
.Fa arg
as its only argument.
.Pp
The
.Fn mountroothook_disestablish
function removes the hook described by the opaque pointer
.Fa cookie
from the list of hooks to be invoked at mountroot.
If
.Fa cookie
is invalid, the result of
.Fn mountroothook_disestablish
is undefined.
.Pp
Mountroot hooks should be used to perform one-time activities
that must happen immediately after the root filesystem has been
mounted by the kernel, but before
.Xr init 8
has been started.
.Pp
Mountroot hooks are, like startup hooks, implemented via the more general
.Xr dohooks 9
API.
.Sh RETURN VALUES
If successful,
.Fn mountroothook_establish
returns an opaque pointer describing the newly established
mountroot hook.
Otherwise, it returns
.Dv NULL .
.Sh EXAMPLES
It may be appropriate to use a mountroot hook to
split the attach function of a device driver.
Once the root filesystem is mounted, the hook will be called
and it is safe to use
.Xr loadfirmware 9
to get the firmware out of the filesystem.
.Sh SEE ALSO
.Xr dohooks 9 ,
.Xr domountroothooks 9 ,
.Xr dostartuphooks 9
.Sh BUGS
The names are clumsy, at best.