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g_attach.9freebsd

Langue: en

Version: 309498 (debian - 07/07/09)

Section: 9 (Appels noyau Linux)


BSD mandoc

NAME

g_attach g_detach - attach/detach GEOM consumers to/from providers

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);
 }
 

ERRORS

Possible errors:
Bq Er ELOOP
The operation creates a topology loop.

SEE ALSO

geom(4), DECLARE_GEOM_CLASS9, g_access9, g_bio9, g_consumer9, g_data9, g_event9, g_geom9, g_provider9, g_provider_by_name9, g_wither_geom9

AUTHORS

An -nosplit This manual page was written by An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
VRRRRRR !

P : Tiens, c'est un portable que tu as dans le cul aujourd'hui ?
M : Oui... Comme un con, j'ai cédé à la mode... J'ai changé mon vibromasseur par un portable avec vibreur...
P : Et alors ?
M : Personne ne m'appelle...