DECLARE_GEOM_CLASS(9)

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