Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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 DEVELOPERS ``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 DEVELOPERS 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: head/share/man/man9/g_consumer.9 127371 2004-03-24 14:25:46Z pjd $

.Dd January 16, 2004 .Dt g_consumer 9 .Os .Sh NAME .Nm g_new_consumer , .Nm g_destroy_consumer .Nd "GEOM consumers management" .Sh SYNOPSIS n geom/geom.h .Ft "struct g_consumer *" .Fn g_new_consumer "struct g_geom *gp" .Ft void .Fn g_destroy_consumer "struct g_consumer *cp" .Sh DESCRIPTION The GEOM consumer is the backdoor through which a geom connects to another GEOM provider and through which I/O requests are sent.

p The .Fn g_new_consumer function creates a new consumer releated to geom .Fa gp . The consumer is unusable prior attaching to a provider and gaining access to it. To serve its purpose, the consumer has to be attached to a provider with the .Xr g_attach 9 function.

p The .Fn g_destroy_consumer function destroys given consumer and cancels all related pending events. This function is the last stage of killing an unwanted consumer.

p .Sh RESTRICTIONS/CONDITIONS .Fn g_new_consumer : l -item -offset indent t The geom related to the created consumer must have the .Fa start and .Fa access fields defined. t The topology lock has to be held. .El

p .Fn g_destroy_consumer : l -item -offset indent t The consumer can not be attached. t The access count has to be 0. t The topology lock has to be held. .El .Sh RETURN VALUES .Fn g_new_consumer returns a pointer to the newly created consumer. .Sh EXAMPLES Create consumer, attach it to given provider, gain read access and clean up. d -literal -offset indent void some_function(struct g_geom *mygeom, struct g_provider *pp) { struct g_consumer *cp; g_topology_assert(); /* Create new consumer on 'mygeom' geom. */ cp = g_new_consumer(mygeom); /* Attach newly created consumer to given provider. */ if (g_attach(cp, pp) != 0) { g_destroy_consumer(cp); return; } /* Open provider for reading through our consumer. */ if (g_access(cp, 1, 0, 0) != 0) { g_detach(cp); g_destroy_consumer(cp); return; } g_topology_unlock(); /* * Read data from provider. */ g_topology_lock(); /* Disconnect from provider (release access count). */ g_access(cp, -1, 0, 0); /* Detach from provider. */ g_detach(cp); /* Destroy consumer. */ g_destroy_consumer(cp); } .Ed .Sh SEE ALSO .Xr DECLARE_GEOM_CLASS 9 , .Xr geom 4 , .Xr g_access 9 , .Xr g_attach 9 , .Xr g_bio 9 , .Xr g_data 9 , .Xr g_event 9 , .Xr g_geom 9 , .Xr g_provider 9 , .Xr g_provider_by_name 9 , .Xr g_wither_geom 9 .Sh AUTHORS .An -nosplit This manual page was written by .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .