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〉.