freebsd/share/man/man9/DECLARE_GEOM_CLASS.9

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.Dd January 16, 2004
.Dt DECLARE_GEOM_CLASS 9
.Os
.Sh NAME
.Nm DECLARE_GEOM_CLASS
.Nd "GEOM class declaration macro"
.Sh SYNOPSIS
.In geom/geom.h
.Fn DECLARE_GEOM_CLASS "class" "mod_name"
.Sh DESCRIPTION
The
.Fn 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.
.Fn DECLARE_GEOM_CLASS
can be used both for compiled in and loaded as
.Xr kld 4
modules GEOM classes and it is the only official way for class registration.
.Pp
The arguments to
.Fn DECLARE_GEOM_CLASS
are:
.Bl -inset -offset indent
.It Em class
is the
.Vt g_class
structure which describes a GEOM class.
.It Em mod_name
is a kernel module name (not a class name!).
.El
.Pp
Structure
.Vt g_class
contains data describing the class.
They are:
.Bl -inset -offset indent
.It Vt "const char *" Va name
Class name.
.It Vt "g_taste_t *" Va taste
Pointer to function used for taste event handling.
If it is
.No non- Ns Dv NULL
it is called in three situations:
.Bl -dash -offset indent -compact
.It
On class activation, all existing providers are offered for tasting.
.It
When new provider is created it is offered for tasting.
.It
After last write access to a provider is closed it is offered for retasting
(on first write open event
.Dq spoil
was sent).
.El
.It Vt "g_config_t *" Va config
This field is not used anymore, its functionality was replaced by the
.Va ctlreq
field.
.It Vt "g_ctl_req_t *" Va ctlreq
Pointer to function used for handling events from userland applications.
.It Vt "g_init_t *" Va init
Pointer to function which is called right after class registration.
.It Vt "g_fini_t *" Va fini
Pointer to function which is called right before class deregistration.
.It Vt "g_ctl_destroy_geom_t *" Va 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.
.El
.Pp
Only field
.Fa name
is required, the rest is optional.
.Pp
.Sh RESTRICTIONS/CONDITIONS
In the
.Vt g_class
initialization one must use C99 initialization (just like in the example below).
.Pp
.Sh EXAMPLES
Example class declaration.
.Bd -literal -offset indent
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);
.Ed
.Sh SEE ALSO
.Xr geom 4 ,
.Xr g_attach 9 ,
.Xr g_bio 9 ,
.Xr g_consumer 9 ,
.Xr g_data 9 ,
.Xr g_event 9 ,
.Xr g_geom 9 ,
.Xr g_provider 9 ,
.Xr g_provider_by_name 9 ,
.Xr g_wither_geom 9
.Sh AUTHORS
.An -nosplit
This manual page was written by
.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .