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 void
             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 int
             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>.

Debian                                           April 24, 2016                                        G_GEOM(9)