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_consumer 9 29.Os 30.Sh NAME 31.Nm g_new_consumer , 32.Nm g_destroy_consumer 33.Nd "GEOM consumers management" 34.Sh SYNOPSIS 35.In geom/geom.h 36.Ft "struct g_consumer *" 37.Fn g_new_consumer "struct g_geom *gp" 38.Ft void 39.Fn g_destroy_consumer "struct g_consumer *cp" 40.Sh DESCRIPTION 41A GEOM consumer is the backdoor through which a geom connects to 42another GEOM provider and through which I/O requests are sent. 43.Pp 44The 45.Fn g_new_consumer 46function creates a new consumer on geom 47.Fa gp . 48Before using the new consumer, it has to be attached to a provider with 49.Xr g_attach 9 50and opened with 51.Xr g_access 9 . 52.Pp 53The 54.Fn g_destroy_consumer 55function destroys the given consumer and cancels all related pending events. 56This function is the last stage of killing an unwanted consumer. 57.Pp 58.Sh RESTRICTIONS/CONDITIONS 59.Fn g_new_consumer : 60.Bl -item -offset indent 61.It 62The geom 63.Fa gp 64has to have 65.Fa start 66and 67.Fa access 68methods defined. 69.It 70The topology lock has to be held. 71.El 72.Pp 73.Fn g_destroy_consumer : 74.Bl -item -offset indent 75.It 76The consumer must not be attached to a provider. 77.It 78The access count has to be 0. 79.It 80The topology lock has to be held. 81.El 82.Sh RETURN VALUES 83.Fn g_new_consumer 84returns a pointer to the newly created consumer. 85.Sh EXAMPLES 86Create consumer, attach it to given provider, gain read access and clean up. 87.Bd -literal -offset indent 88void 89some_function(struct g_geom *mygeom, struct g_provider *pp) 90{ 91 struct g_consumer *cp; 92 93 g_topology_assert(); 94 95 /* Create new consumer on 'mygeom' geom. */ 96 cp = g_new_consumer(mygeom); 97 /* Attach newly created consumer to given provider. */ 98 if (g_attach(cp, pp) != 0) { 99 g_destroy_consumer(cp); 100 return; 101 } 102 /* Open provider for reading through our consumer. */ 103 if (g_access(cp, 1, 0, 0) != 0) { 104 g_detach(cp); 105 g_destroy_consumer(cp); 106 return; 107 } 108 109 g_topology_unlock(); 110 /* 111 * Read data from provider. 112 */ 113 g_topology_lock(); 114 115 /* Disconnect from provider (release access count). */ 116 g_access(cp, -1, 0, 0); 117 /* Detach from provider. */ 118 g_detach(cp); 119 /* Destroy consumer. */ 120 g_destroy_consumer(cp); 121} 122.Ed 123.Sh SEE ALSO 124.Xr DECLARE_GEOM_CLASS 9 , 125.Xr geom 4 , 126.Xr g_access 9 , 127.Xr g_attach 9 , 128.Xr g_bio 9 , 129.Xr g_data 9 , 130.Xr g_event 9 , 131.Xr g_geom 9 , 132.Xr g_provider 9 , 133.Xr g_provider_by_name 9 , 134.Xr g_wither_geom 9 135.Sh AUTHORS 136.An -nosplit 137This manual page was written by 138.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . 139