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 consumer to/from provider" 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 to given provider. 44For real provider access (ie. I/O operations), one still need to call the 45.Fn g_access 46function on consumer to gain access to attached provider. 47.Pp 48The 49.Fn g_detach 50function detaches the given consumer from the corresponding provider. 51This function is used when we do not want to communicate with the 52provider anymore. 53.Sh RESTRICTIONS/CONDITIONS 54.Fn g_attach : 55.Bl -item -offset indent 56.It 57The consumer can not be attached already. 58.It 59The operation should not create a topology loop. 60.It 61The topology lock has to be held. 62.El 63.Pp 64.Fn g_detach : 65.Bl -item -offset indent 66.It 67The consumer has to be attached. 68.It 69The access count has to be 0. 70.It 71There must be no active requests. 72.It 73The topology lock has to be held. 74.El 75.Sh RETURN VALUES 76.Fn g_attach 77returns the value 0 if successful; otherwise an error code is returned. 78.Sh ERRORS 79Possible errors: 80.Bl -tag -width Er 81.It Bq Er ELOOP 82The operation creates a topology loop. 83.El 84.Sh EXAMPLES 85Create consumer, attach it to given provider, gain read access and clean up. 86.Bd -literal -offset indent 87void 88some_function(struct g_geom *mygeom, struct g_provider *pp) 89{ 90 struct g_consumer *cp; 91 92 g_topology_assert(); 93 94 /* Create new consumer on 'mygeom' geom. */ 95 cp = g_new_consumer(mygeom); 96 /* Attach newly created consumer to given provider. */ 97 if (g_attach(cp, pp) != 0) { 98 g_destroy_consumer(cp); 99 return; 100 } 101 /* Open provider for reading through our consumer. */ 102 if (g_access(cp, 1, 0, 0) != 0) { 103 g_detach(cp); 104 g_destroy_consumer(cp); 105 return; 106 } 107 108 g_topology_unlock(); 109 /* 110 * Read data from provider. 111 */ 112 g_topology_lock(); 113 114 /* Disconnect from provider (release access count). */ 115 g_access(cp, -1, 0, 0); 116 /* Detach from provider. */ 117 g_detach(cp); 118 /* Destroy consumer. */ 119 g_destroy_consumer(cp); 120} 121.Ed 122.Sh SEE ALSO 123.Xr DECLARE_GEOM_CLASS 9 , 124.Xr geom 4 , 125.Xr g_access 9 , 126.Xr g_bio 9 , 127.Xr g_consumer 9 , 128.Xr g_data 9 , 129.Xr g_event 9 , 130.Xr g_geom 9 , 131.Xr g_provider 9 , 132.Xr g_provider_by_name 9 , 133.Xr g_wither_geom 9 134.Sh AUTHORS 135.An -nosplit 136This manual page was written by 137.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . 138