$OpenBSD: hook_establish.9,v 1.12 2015/12/12 11:26:32 mpi Exp $
Copyright (c) 2001 Niklas Hallqvist.
All rights reserved.
Redistribution and use in source and binary forms, with or without
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.Dd $Mdocdate: December 10 2014 $ .Dt HOOK_ESTABLISH 9 .Os .Sh NAME .Nm hook_establish , .Nm hook_disestablish .Nd add or remove a hook from a specified list .Sh SYNOPSIS n sys/types.h n sys/systm.h .Ft void * .Fn hook_establish "struct hook_desc_head *head" "int tail" "void (*fn)(void *)" "void *arg" .Ft void .Fn hook_disestablish "struct hook_desc_head *head" "void *cookie" .Sh DESCRIPTION The .Fn hook_establish function adds .Fa fn to the list of hooks invoked by .Xr dohooks 9 . If .Fa tail is non-zero, the hook is added to the tail of the list denoted by the TAILQ_HEAD pointer .Fa head , otherwise to the front. The .Xr dohooks 9 function will at its invocation call each hook from the front of this list. When invoked, the hook function .Fa fn will be passed .Fa arg as its only argument.
Copyright (c) 2001 Niklas Hallqvist.
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.
3. The name of the author may not be used to endorse or promote products
derived from this software without specific prior written permission
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
.Dd $Mdocdate: December 10 2014 $ .Dt HOOK_ESTABLISH 9 .Os .Sh NAME .Nm hook_establish , .Nm hook_disestablish .Nd add or remove a hook from a specified list .Sh SYNOPSIS n sys/types.h n sys/systm.h .Ft void * .Fn hook_establish "struct hook_desc_head *head" "int tail" "void (*fn)(void *)" "void *arg" .Ft void .Fn hook_disestablish "struct hook_desc_head *head" "void *cookie" .Sh DESCRIPTION The .Fn hook_establish function adds .Fa fn to the list of hooks invoked by .Xr dohooks 9 . If .Fa tail is non-zero, the hook is added to the tail of the list denoted by the TAILQ_HEAD pointer .Fa head , otherwise to the front. The .Xr dohooks 9 function will at its invocation call each hook from the front of this list. When invoked, the hook function .Fa fn will be passed .Fa arg as its only argument.
p The .Fn hook_disestablish function removes the hook described by the opaque pointer .Fa cookie from the list of hooks denoted by the TAILQ_HEAD pointer .Fa head . If .Fa cookie is invalid, the result of .Fn hook_disestablish is undefined.
p The startup and mountroot systems use this API for their implementation. .Sh RETURN VALUES If successful, .Fn hook_establish returns an opaque pointer describing the newly established hook. Otherwise, it returns .Dv NULL . .Sh SEE ALSO .Xr dohooks 9 , .Xr dostartuphooks 9 , .Xr startuphook_establish 9