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G_CONSUMER(9)		    Kernel Developer's Manual		   G_CONSUMER(9)

NAME
     g_new_consumer, g_destroy_consumer -- GEOM consumers management

SYNOPSIS
     #include <geom/geom.h>

     struct g_consumer *
     g_new_consumer(struct g_geom *gp);

     void
     g_destroy_consumer(struct g_consumer *cp);

DESCRIPTION
     A	GEOM  consumer	is the backdoor through which a geom connects to another
     GEOM provider and through which I/O requests are sent.

     The g_new_consumer() function creates a new consumer on  geom  gp.   Before
     using  the  new  consumer,  it  has to be attached to a provider with g_at-
     tach(9) and opened with g_access(9).

     The 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.

RESTRICTIONS/CONDITIONS
     g_new_consumer():

	   The geom gp has to have an orphan method defined.

	   The topology lock has to be held.

     g_destroy_consumer():

	   The consumer must not be attached to a provider.

	   The access count has to be 0.

	   The topology lock has to be held.

RETURN VALUES
     The g_new_consumer() function returns a pointer to the newly  created  con-
     sumer.

EXAMPLES
     Create  consumer,	attach	it to given provider, gain read access and clean
     up.

	   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);
	   }

SEE ALSO
     geom(4),	DECLARE_GEOM_CLASS(9),	 g_access(9),	g_attach(9),   g_bio(9),
     g_data(9),  g_event(9),  g_geom(9),  g_provider(9),  g_provider_by_name(9),
     g_wither_geom(9)

AUTHORS
     This manual page was written by Pawel Jakub Dawidek <pjd@FreeBSD.org>.

FreeBSD ports 15.quarterly	January 16, 2004		   G_CONSUMER(9)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=g_consumer&sektion=9&manpath=FreeBSD+15.1-RELEASE+and+Ports.quarterly>

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