Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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$FreeBSD: releng/11.0/share/man/man9/g_consumer.9 267936 2014-06-26 21:44:30Z bapt $
.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 A 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 on geom .Fa gp . Before using the new consumer, it has to be attached to a provider with .Xr g_attach 9 and opened with .Xr g_access 9 .
p The .Fn g_destroy_consumer function destroys the given consumer and cancels all related pending events. This function is the last stage of killing an unwanted consumer. .Sh RESTRICTIONS/CONDITIONS .Fn g_new_consumer : l -item -offset indent t The geom .Fa gp has to have an .Va orphan method defined. t The topology lock has to be held. .El
p .Fn g_destroy_consumer : l -item -offset indent t The consumer must not be attached to a provider. t The access count has to be 0. t The topology lock has to be held. .El .Sh RETURN VALUES The .Fn g_new_consumer function 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 geom 4 , .Xr DECLARE_GEOM_CLASS 9 , .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 Mt pjd@FreeBSD.org .