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>.