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);
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_wither_geom(9)
AUTHORS¶
This manual page was written by
Pawel Jakub Dawidek
⟨pjd@FreeBSD.org⟩.