SYNOPSIS

In geom/geom.h Ft int Fn g_attach struct g_consumer *cp struct g_provider *pp Ft void Fn g_detach struct g_consumer *cp

DESCRIPTION

The Fn g_attach function attaches given consumer Fa cp to given provider Fa pp , thus establishing a communication channel between the consumer and the provider that allows to change access counts and perform I/O operations.

The Fn g_detach function detaches given consumer Fa cp from its corresponding provider, tearing down the communication channel between them.

RESTRICTIONS/CONDITIONS

Fn g_attach :

The consumer must not be attached to a provider.

The operation must not create a topology loop.

The topology lock has to be held.

Fn g_detach :

The consumer has to be attached.

The access count has to be 0.

There must be no active requests.

The topology lock has to be held.

RETURN VALUES

The Fn g_attach function returns 0 if successful; otherwise an error code is returned.

EXAMPLES

Create a consumer, attach it to a given provider, gain read access and clean up.

void
some_function(struct g_geom *mygeom, struct g_provider *pp)
{
        struct g_consumer *cp;
        g_topology_assert();
        /* Create new consumer on 'mygeom' geom. */
        cp = g_new_consumer(mygeom);
        /* Attach newly created consumer to given provider. */
        if (g_attach(cp, pp) != 0) {
                g_destroy_consumer(cp);
                return;
        }
        /* Open provider for reading through our consumer. */
        if (g_access(cp, 1, 0, 0) != 0) {
                g_detach(cp);
                g_destroy_consumer(cp);
                return;
        }
        g_topology_unlock();
        /*
         * Read data from provider.
         */
        g_topology_lock();
        /* Disconnect from provider (release access count). */
        g_access(cp, -1, 0, 0);
        /* Detach from provider. */
        g_detach(cp);
        /* Destroy consumer. */
        g_destroy_consumer(cp);
}

AUTHORS

An -nosplit This manual page was written by An Pawel Jakub Dawidek Aq [email protected] .