declare_geom_class(9)

NAME

DECLARE_GEOM_CLASS - GEOM class declaration macro

SYNOPSIS

#include <geom/geom.h>
DECLARE_GEOM_CLASS(class, mod_name);

DESCRIPTION

The DECLARE_GEOM_CLASS() macro registers a GEOM class in GE

OM. A GEOM
class itself implements one particular kind of transforma

tion. Typical
examples are: MBR disk partition, BSD disklabel and RAID5

classes.
DECLARE_GEOM_CLASS() can be used both for compiled in and

loaded as
kld(4) modules GEOM classes and it is the only official way

for class
registration.

The arguments to DECLARE_GEOM_CLASS() are:

class The g_class structure which describes a

GEOM class.

mod_name A kernel module name (not a class

name!).

Structure g_class contains data describing the class. They

are:

const char * name

Class name.

g_taste_t * taste

Pointer to function used for taste event han

dling. If it
is non-NULL it is called in three situations:

- On class activation, all existing

providers are offered

for tasting.

- When new provider is created it is offered

for tasting.
- After last write access to a provider is

closed it is

offered for retasting (on first write open

event
``spoil'' was sent).

g_config_t * config

This field is not used anymore, its function

ality was
replaced by the ctlreq field.

g_ctl_req_t * ctlreq

Pointer to function used for handling events

from userland
applications.

g_init_t * init

Pointer to function which is called right af

ter class registration.

g_fini_t * fini

Pointer to function which is called right be

fore class
deregistration.

g_ctl_destroy_geom_t * destroy_geom

Pointer to a function which is called for ev

ery geom on
class unload. If this field is not set, the

class can not
be unloaded.

Only a name field is required; the rest are optional.

RESTRICTIONS/CONDITIONS

The fields of g_class should always be initialized using

C99-style field
naming (see the initialization of example_class below).

EXAMPLES

Example class declaration.

static struct geom *
g_example_taste(struct g_class *mp, struct g_provider

*pp,

int flags __unused)

{

g_topology_assert();

[...]

}

static void
g_example_ctlreq(struct gctl_req *req, struct g_class

*cp,

char const *verb)

{

[...]

}

static int
g_example_destroy_geom(struct gctl_req *req, struct

g_class *cp,

struct g_geom *gp)

{

g_topology_assert();

[...]

}

static void
g_example_init(struct g_class *mp)
{

[...]

}

static void
g_example_fini(struct g_class *mp)
{

[...]

}

struct g_class example_class = {

.name = "EXAMPLE",
.taste = g_example_taste,
.ctlreq = g_example_ctlreq,
.init = g_example_init,
.fini = g_example_fini,
.destroy_geom = g_example_destroy_geom

};

DECLARE_GEOM_CLASS(example_class, g_example);

SEE ALSO

geom(4), g_attach(9), g_bio(9), g_consumer(9), g_data(9),

g_event(9),
g_geom(9), g_provider(9), g_provider_by_name(9), g_with

er_geom(9)

AUTHORS

This manual page was written by Pawel Jakub Dawidek

<pjd@FreeBSD.org>.

BSD January 6, 2005

BSD