NAME

       g_new_providerf, g_destroy_provider, g_error_provider — GEOM providers management

SYNOPSIS

       #include <geom/geom.h>

       struct g_provider *
       g_new_providerf(struct g_geom *gp, const char *fmt, ...);

       void
       g_destroy_provider(struct g_provider *pp);

       void
       g_error_provider(struct g_provider *pp, int error);

DESCRIPTION

       A GEOM provider is the front gate at which a geom offers service.  A provider is “a disk-like thing which
       appears  in  /dev”  –  a  logical  disk  in other words.  All providers have three main properties: name,
       sectorsize and size.

       The g_new_providerf() function creates a new provider on given geom gp.  The name of the provider,  which
       will  appear  as  device  in devfs(5), is created in a printf(3)-like way from the rest of the arguments.
       After creation, the caller has to set the provider's mediasize and sectorsize, as well as  other  desired
       initializations,  and  then call g_error_provider() to reset the provider's error, which is initially set
       to ENXIO.

       The g_destroy_provider() function destroys the given provider, cancels all  related  pending  events  and
       removes the corresponding devfs entry.

       The  g_error_provider() function is used to set the provider's error value.  If set to a nonzero, all I/O
       requests will be denied, as well as increasing its access count will not be possible (error error will be
       returned).

RESTRICTIONS/CONDITIONS

       g_new_provider():

             The provider name should be unique, but this is not enforced by GEOM.  If the name is  not  unique,
             one will end up with two (or more) files with the same name, which is a programmer error.

             The geom gp has to have a start method defined.

             The topology lock has to be held.

       g_destroy_provider():

             The provider must not have consumers attached.

             The access count has to be 0.

             The topology lock has to be held.

RETURN VALUES

       The g_new_providerf() function returns a pointer to the newly created provider.

EXAMPLES

       Create an example provider, set its parameters and make it usable.

             struct g_provider *
             create_example_provider(struct g_geom *gp)
             {
                     struct g_provider *pp;

                     g_topology_lock();
                     pp = g_new_providerf(gp, "example_provider");
                     g_topology_unlock();
                     pp->mediasize = 65536;
                     pp->sectorsize = 512;
                     g_error_provider(pp, 0);

                     return (pp);
             }

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_geom(9), g_provider_by_name(9), g_wither_geom(9)

AUTHORS

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

Debian                                          January 16, 2004                                   G_PROVIDER(9)