freebsd-dev/share/man/man9/g_geom.9

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.Dd January 16, 2004
.Dt G_GEOM 9
.Os
.Sh NAME
.Nm g_new_geomf ,
.Nm g_destroy_geom
.Nd "geom management"
.Sh SYNOPSIS
.In geom/geom.h
.Ft "struct g_geom *"
.Fn g_new_geomf "struct g_class *mp" "const char *fmt" ...
.Ft void
.Fn g_destroy_geom "struct g_geom *gp"
.Sh DESCRIPTION
The geom (do not confuse
.Dq geom
with
.Dq GEOM )
is an instance of a GEOM class.
For example: in a typical i386
.Fx
system, there will be one geom
of class MBR for each disk.
The geom's name is not really important, it is only used in the XML
dump and for debugging purposes.
There can be many geoms with the same name.
.Pp
The
.Fn g_new_geomf
function creates a new geom, which will be an instance of the class
.Fa mp .
The geom's name is created in a
.Xr printf 3 Ns
-like way from the rest of the arguments.
.Pp
The
.Fn g_destroy_geom
function destroys the given geom immediately and cancels all related pending
events.
.Pp
The
.Vt g_geom
structure
contains fields that should be set by the caller after geom creation, but before
creating any providers or consumers related to this geom (not all are required):
.Bl -tag -offset indent -width indent
.It Vt "g_start_t *" Va start
Pointer to a function used for I/O processing.
.It Vt "g_spoiled_t *" Va spoiled
Pointer to a function used for consumers spoiling.
.It Vt "g_dumpconf_t *" Va dumpconf
Pointer to a function used for configuration in XML format dumping.
.It Vt "g_access_t *" Va access
Pointer to a function used for access control.
.It Vt "g_orphan_t *" Va orphan
Pointer to a function used to inform about orphaned consumer.
.It Vt "g_ioctl_t *" Va ioctl
Pointer to a function used for handling ioctl requests.
.It Vt "void *" Va softc
Field for private use.
.El
.Sh RESTRICTIONS/CONDITIONS
If you intend to use providers in this geom you must set field
.Va start
of your geom.
.Pp
If you are planning to use consumers in your geom you must set fields
.Va orphan
and
.Va access
for it.
.Pp
.Fn g_new_geomf :
.Bl -item -offset indent
.It
Class
.Fa mp
must be valid (registered in GEOM).
.It
The topology lock has to be held.
.El
.Pp
.Fn g_destroy_geom :
.Bl -item -offset indent
.It
The geom cannot posses any providers.
.It
The geom cannot posses any consumers.
.It
The topology lock has to be held.
.El
.Sh RETURN VALUES
The
.Fn g_new_geomf
function
returns a pointer to the newly created geom.
.Sh EXAMPLES
Create an example geom.
.Bd -literal -offset indent
static struct geom *
g_example_start(struct bio *bp)
{

	[...]
}

static void
g_example_orphan(struct g_consumer *cp)
{

	g_topology_assert();

	[...]
}

static void
g_example_spoiled(struct g_consumer *cp)
{

	g_topology_assert();

	[...]
}

static void
g_example_access(struct g_provider *pp, int dr, int dw, int de)
{

	[...]
}

static struct g_geom *
create_example_geom(struct g_class *myclass)
{
	struct g_geom *gp;

	g_topology_lock();
	gp = g_new_geomf(myclass, "example_geom");
	g_topology_unlock();
	gp->start = g_example_start;
	gp->orphan = g_example_orphan;
	gp->spoiled = g_example_spoiled;
	gp->access = g_example_access;
	gp->softc = NULL;

	return (gp);
}

static int
destroy_example_geom(struct g_geom *gp)
{

	g_topology_lock();
	if (!LIST_EMPTY(&gp->provider) ||
	    !LIST_EMPTY(&gp->consumer)) {
		g_topology_unlock();
		return (EBUSY);
	}
	g_destroy_geom(gp);
	g_topology_unlock();

	return (0);
}
.Ed
.Sh SEE ALSO
.Xr geom 4 ,
.Xr DECLARE_GEOM_CLASS 9 ,
.Xr g_access 9 ,
.Xr g_attach 9 ,
.Xr g_bio 9 ,
.Xr g_consumer 9 ,
.Xr g_data 9 ,
.Xr g_event 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 .