1.\" 2.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 15.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 18.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd January 16, 2004 28.Dt G_ATTACH 9 29.Os 30.Sh NAME 31.Nm g_attach , 32.Nm g_detach 33.Nd "attach/detach GEOM consumers to/from providers" 34.Sh SYNOPSIS 35.In geom/geom.h 36.Ft int 37.Fn g_attach "struct g_consumer *cp" "struct g_provider *pp" 38.Ft void 39.Fn g_detach "struct g_consumer *cp" 40.Sh DESCRIPTION 41The 42.Fn g_attach 43function attaches given consumer 44.Fa cp 45to given provider 46.Fa pp , 47thus establishing a communication channel between the consumer and the 48provider that allows to change access counts and perform I/O operations. 49.Pp 50The 51.Fn g_detach 52function detaches given consumer 53.Fa cp 54from its corresponding provider, tearing down the communication channel 55between them. 56.Sh RESTRICTIONS/CONDITIONS 57.Fn g_attach : 58.Bl -item -offset indent 59.It 60The consumer must not be attached to a provider. 61.It 62The operation must not create a topology loop. 63.It 64The topology lock has to be held. 65.El 66.Pp 67.Fn g_detach : 68.Bl -item -offset indent 69.It 70The consumer has to be attached. 71.It 72The access count has to be 0. 73.It 74There must be no active requests. 75.It 76The topology lock has to be held. 77.El 78.Sh RETURN VALUES 79The 80.Fn g_attach 81function returns 0 if successful; otherwise an error code is returned. 82.Sh ERRORS 83Possible errors: 84.Bl -tag -width Er 85.It Bq Er ELOOP 86The operation creates a topology loop. 87.El 88.Sh EXAMPLES 89Create a consumer, attach it to a given provider, gain read access and clean up. 90.Bd -literal -offset indent 91void 92some_function(struct g_geom *mygeom, struct g_provider *pp) 93{ 94 struct g_consumer *cp; 95 96 g_topology_assert(); 97 98 /* Create new consumer on 'mygeom' geom. */ 99 cp = g_new_consumer(mygeom); 100 /* Attach newly created consumer to given provider. */ 101 if (g_attach(cp, pp) != 0) { 102 g_destroy_consumer(cp); 103 return; 104 } 105 /* Open provider for reading through our consumer. */ 106 if (g_access(cp, 1, 0, 0) != 0) { 107 g_detach(cp); 108 g_destroy_consumer(cp); 109 return; 110 } 111 112 g_topology_unlock(); 113 /* 114 * Read data from provider. 115 */ 116 g_topology_lock(); 117 118 /* Disconnect from provider (release access count). */ 119 g_access(cp, -1, 0, 0); 120 /* Detach from provider. */ 121 g_detach(cp); 122 /* Destroy consumer. */ 123 g_destroy_consumer(cp); 124} 125.Ed 126.Sh SEE ALSO 127.Xr geom 4 , 128.Xr DECLARE_GEOM_CLASS 9 , 129.Xr g_access 9 , 130.Xr g_bio 9 , 131.Xr g_consumer 9 , 132.Xr g_data 9 , 133.Xr g_event 9 , 134.Xr g_geom 9 , 135.Xr g_provider 9 , 136.Xr g_provider_by_name 9 , 137.Xr g_wither_geom 9 138.Sh AUTHORS 139.An -nosplit 140This manual page was written by 141.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . 142