freebsd man page for g_geom

G_GEOM(9)						   BSD Kernel Developer's Manual						 G_GEOM(9)

NAME
     g_new_geomf, g_destroy_geom -- geom management

SYNOPSIS
     #include <geom/geom.h>

     struct g_geom *
     g_new_geomf(struct g_class *mp, const char *fmt, ...);

     void
     g_destroy_geom(struct g_geom *gp);

DESCRIPTION
     The geom (do not confuse ``geom'' with ``GEOM'') is an instance of a GEOM class.  For example: in a typical i386 FreeBSD system, there will
     be one geom of class MBR for each disk.  The geom's name is not really important, it is only used in the XML dump and for debugging purposes.
     There can be many geoms with the same name.

     The g_new_geomf() function creates a new geom, which will be an instance of the class mp.	The geom's name is created in a printf(3)-like way
     from the rest of the arguments.

     The g_destroy_geom() function destroys the given geom immediately and cancels all related pending events.

     The g_geom structure contains fields that should be set by the caller after geom creation, but before creating any providers or consumers
     related to this geom (not all are required):

	   g_start_t * start
		   Pointer to a function used for I/O processing.

	   g_spoiled_t * spoiled
		   Pointer to a function used for consumers spoiling.

	   g_dumpconf_t * dumpconf
		   Pointer to a function used for configuration in XML format dumping.

	   g_access_t * access
		   Pointer to a function used for access control.

	   g_orphan_t * orphan
		   Pointer to a function used to inform about orphaned consumer.

	   g_ioctl_t * ioctl
		   Pointer to a function used for handling ioctl requests.

	   void * softc
		   Field for private use.

RESTRICTIONS
/CONDITIONS
     If you intend to use providers in this geom you must set field start of your geom.

     If you are planning to use consumers in your geom you must set fields orphan and access for it.

     g_new_geomf():

	   Class mp must be valid (registered in GEOM).

	   The topology lock has to be held.

     g_destroy_geom():

	   The geom cannot possess any providers.

	   The geom cannot possess any consumers.

	   The topology lock has to be held.

RETURN VALUES
     The g_new_geomf() function returns a pointer to the newly created geom.

EXAMPLES
     Create an example geom.

	   static struct geom *
	   g_example_start(struct bio *bp)
	   {

		   [...]
	   }

	   static void
	   g_example_orphan(struct g_consumer *cp)
	   {

		   g_topology_assert();

		   [...]
	   }

	   static void
	   g_example_spoiled(struct g_consumer *cp)
	   {

		   g_topology_assert();

		   [...]
	   }

	   static void
	   g_example_access(struct g_provider *pp, int dr, int dw, int de)
	   {

		   [...]
	   }

	   static struct g_geom *
	   create_example_geom(struct g_class *myclass)
	   {
		   struct g_geom *gp;

		   g_topology_lock();
		   gp = g_new_geomf(myclass, "example_geom");
		   g_topology_unlock();
		   gp->start = g_example_start;
		   gp->orphan = g_example_orphan;
		   gp->spoiled = g_example_spoiled;
		   gp->access = g_example_access;
		   gp->softc = NULL;

		   return (gp);
	   }

	   static int
	   destroy_example_geom(struct g_geom *gp)
	   {

		   g_topology_lock();
		   if (!LIST_EMPTY(&gp->provider) ||
		       !LIST_EMPTY(&gp->consumer)) {
			   g_topology_unlock();
			   return (EBUSY);
		   }
		   g_destroy_geom(gp);
		   g_topology_unlock();

		   return (0);
	   }

SEE ALSO
     geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9), g_bio(9), g_consumer(9), g_data(9), g_event(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>.

BSD
								 January 16, 2004							       BSD