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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 posses any providers.

           The geom cannot posses 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〉.