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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〉.