06bb88dcb2
- g_new_geomf(), - g_new_providerf(), - g_new_consumer() cannot failed (by returning NULL), so don't scare programmers.
138 lines
3.7 KiB
Groff
138 lines
3.7 KiB
Groff
.\"
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.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 16, 2004
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.Dt g_attach 9
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.Os
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.Sh NAME
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.Nm g_attach ,
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.Nm g_detach
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.Nd "attach/detach consumer to/from provider"
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.Sh SYNOPSIS
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.In geom/geom.h
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.Ft int
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.Fn g_attach "struct g_consumer *cp" "struct g_provider *pp"
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.Ft void
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.Fn g_detach "struct g_consumer *cp"
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.Sh DESCRIPTION
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The
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.Fn g_attach
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function attaches given consumer to given provider.
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For real provider access (ie. I/O operations), one still need to call the
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.Fn g_access
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function on consumer to gain access to attached provider.
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.Pp
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The
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.Fn g_detach
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function detaches the given consumer from the corresponding provider.
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This function is used when we do not want to communicate with the
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provider anymore.
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.Sh RESTRICTIONS/CONDITIONS
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.Fn g_attach :
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.Bl -item -offset indent
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.It
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The consumer can not be attached already.
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.It
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The operation should not create a topology loop.
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.It
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The topology lock has to be held.
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.El
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.Pp
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.Fn g_detach :
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.Bl -item -offset indent
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.It
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The consumer has to be attached.
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.It
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The access count has to be 0.
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.It
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There must be no active requests.
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.It
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The topology lock has to be held.
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.El
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.Sh RETURN VALUES
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.Fn g_attach
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returns the value 0 if successful; otherwise an error code is returned.
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.Sh ERRORS
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Possible errors:
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.Bl -tag -width Er
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.It Bq Er ELOOP
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The operation creates a topology loop.
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.El
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.Sh EXAMPLES
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Create consumer, attach it to given provider, gain read access and clean up.
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.Bd -literal -offset indent
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void
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some_function(struct g_geom *mygeom, struct g_provider *pp)
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{
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struct g_consumer *cp;
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g_topology_assert();
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/* Create new consumer on 'mygeom' geom. */
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cp = g_new_consumer(mygeom);
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/* Attach newly created consumer to given provider. */
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if (g_attach(cp, pp) != 0) {
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g_destroy_consumer(cp);
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return;
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}
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/* Open provider for reading through our consumer. */
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if (g_access(cp, 1, 0, 0) != 0) {
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g_detach(cp);
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g_destroy_consumer(cp);
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return;
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}
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g_topology_unlock();
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/*
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* Read data from provider.
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*/
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g_topology_lock();
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/* Disconnect from provider (release access count). */
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g_access(cp, -1, 0, 0);
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/* Detach from provider. */
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g_detach(cp);
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/* Destroy consumer. */
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g_destroy_consumer(cp);
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}
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.Ed
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.Sh SEE ALSO
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.Xr DECLARE_GEOM_CLASS 9 ,
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.Xr geom 4 ,
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.Xr g_access 9 ,
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.Xr g_bio 9 ,
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.Xr g_consumer 9 ,
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.Xr g_data 9 ,
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.Xr g_event 9 ,
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.Xr g_geom 9 ,
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.Xr g_provider 9 ,
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.Xr g_provider_by_name 9 ,
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.Xr g_wither_geom 9
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.Sh AUTHORS
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.An -nosplit
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This manual page was written by
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.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
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