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.Dd October 10, 2020 26.Dt G_ATTACH 9 27.Os 28.Sh NAME 29.Nm g_attach , 30.Nm g_detach 31.Nd "attach/detach GEOM consumers to/from providers" 32.Sh SYNOPSIS 33.In geom/geom.h 34.Ft int 35.Fn g_attach "struct g_consumer *cp" "struct g_provider *pp" 36.Ft void 37.Fn g_detach "struct g_consumer *cp" 38.Sh DESCRIPTION 39The 40.Fn g_attach 41function attaches given consumer 42.Fa cp 43to given provider 44.Fa pp , 45thus establishing a communication channel between the consumer and the 46provider that allows to change access counts and perform I/O operations. 47.Pp 48The 49.Fn g_detach 50function detaches given consumer 51.Fa cp 52from its corresponding provider, tearing down the communication channel 53between them. 54.Sh RESTRICTIONS/CONDITIONS 55.Fn g_attach : 56.Bl -item -offset indent 57.It 58The consumer must not be attached to a provider. 59.It 60The operation must not create a topology loop. 61.It 62The topology lock has to be held. 63.El 64.Pp 65.Fn g_detach : 66.Bl -item -offset indent 67.It 68The consumer has to be attached. 69.It 70The access count has to be 0. 71.It 72There must be no active requests. 73.It 74The topology lock has to be held. 75.El 76.Sh RETURN VALUES 77The 78.Fn g_attach 79function returns 0 if successful; otherwise an error code is returned. 80.Sh EXAMPLES 81Create a consumer, attach it to a given provider, gain read access and clean up. 82.Bd -literal -offset indent 83void 84some_function(struct g_geom *mygeom, struct g_provider *pp) 85{ 86 struct g_consumer *cp; 87 88 g_topology_assert(); 89 90 /* Create new consumer on 'mygeom' geom. */ 91 cp = g_new_consumer(mygeom); 92 /* Attach newly created consumer to given provider. */ 93 if (g_attach(cp, pp) != 0) { 94 g_destroy_consumer(cp); 95 return; 96 } 97 /* Open provider for reading through our consumer. */ 98 if (g_access(cp, 1, 0, 0) != 0) { 99 g_detach(cp); 100 g_destroy_consumer(cp); 101 return; 102 } 103 104 g_topology_unlock(); 105 /* 106 * Read data from provider. 107 */ 108 g_topology_lock(); 109 110 /* Disconnect from provider (release access count). */ 111 g_access(cp, -1, 0, 0); 112 /* Detach from provider. */ 113 g_detach(cp); 114 /* Destroy consumer. */ 115 g_destroy_consumer(cp); 116} 117.Ed 118.Sh ERRORS 119Possible errors: 120.Bl -tag -width Er 121.It Bq Er ELOOP 122The operation creates a topology loop. 123.It Bq Er ENXIO 124Provider got orphaned. 125.El 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 Mt pjd@FreeBSD.org . 142