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DECLARE_GEOM_CLASS – GEOM class declaration macro



#include <geom/geom.h>

DECLARE_GEOM_CLASS(class, mod_name);


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.


The fields of g_class should always be initialized using C99-style field naming (see the initialization of example_class below).


Example class declaration.
static struct g_geom *
g_example_taste(struct g_class *mp, struct g_provider *pp,
    int flags __unused)

        [...] }

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) {


        [...] }

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);


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)


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

DECLARE_GEOM_CLASS (9) August 13, 2007

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