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 GEOM. A GEOM class itself implements one particular kind of transformation. 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 handling. 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 functionality 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 after class registration.

g_fini_t * fini

Pointer to function which is called right before class deregistration.

g_ctl_destroy_geom_t * destroy_geom

Pointer to a function which is called for every 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 g_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);

AUTHORS

This manual page was written by Pawel Jakub Dawidek <pjd@FreeBSD.org>.

August 13, 2007

Debian