Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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$FreeBSD: head/share/man/man9/g_attach.9 126861 2004-03-11 19:53:22Z pjd $

.Dd January 16, 2004 .Dt g_attach 9 .Os .Sh NAME .Nm g_attach , .Nm g_detach .Nd "attach/detach consumer to/from provider" .Sh SYNOPSIS n geom/geom.h .Ft int .Fn g_attach "struct g_consumer *cp" "struct g_provider *pp" .Ft void .Fn g_detach "struct g_consumer *cp" .Sh DESCRIPTION The .Fn g_attach function attaches given consumer to given provider. For real provider access (ie. I/O operations), one still need to call the .Fn g_access function on consumer to gain access to attached provider.

p The .Fn g_detach function detaches the given consumer from the corresponding provider. This function is used when we do not want to communicate with the provider anymore. .Sh RESTRICTIONS/CONDITIONS .Fn g_attach : l -item -offset indent t The consumer can not be attached already. t The operation should not create a topology loop. t The topology lock has to be held. .El

p .Fn g_detach : l -item -offset indent t The consumer has to be attached. t The access count has to be 0. t There must be no active requests. t The topology lock has to be held. .El .Sh RETURN VALUES .Fn g_attach returns the value 0 if successful; otherwise an error code is returned. .Sh ERRORS Possible errors: l -tag -width Er t Bq Er ELOOP The operation creates a topology loop. .El .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); if (cp == NULL) return; /* 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 DECLARE_GEOM_CLASS 9 , .Xr geom 4 , .Xr g_access 9 , .Xr g_bio 9 , .Xr g_consumer 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 pjd@FreeBSD.org .