g_provider(9)

NAME

g_new_providerf, g_destroy_provider, g_error_provider - GEOM

providers
management

SYNOPSIS

#include <geom/geom.h>
struct g_provider *
g_new_providerf(struct g_geom *gp, const char *fmt, ...);
void
g_destroy_provider(struct g_provider *pp);
void
g_error_provider(struct g_provider *pp, int error);

DESCRIPTION

A GEOM provider is the front gate at which a geom offers

service. A
provider is ``a disk-like thing which appears in /dev'' - a

logical disk
in other words. All providers have three main properties:

name, sectorsize and size.

The g_new_providerf() function creates a new provider on

given geom gp.
The name of the provider, which will appear as device in de

vfs(5), is
created in a printf(3)-like way from the rest of the argu

ments. After
creation, the caller has to set the provider's mediasize and

sectorsize,
as well as other desired initializations, and then call
g_error_provider() to reset the provider's error, which is

initially set
to ENXIO.

The g_destroy_provider() function destroys the given

provider, cancels
all related pending events and removes the corresponding de

vfs entry.

The g_error_provider() function is used to set the

provider's error
value. If set to a nonzero, all I/O requests will be de

nied, as well as
increasing its access count will not be possible (error

error will be
returned).

RESTRICTIONS/CONDITIONS

g_new_provider():

The provider name should be unique, but this is not

enforced by
GEOM. If the name is not unique, one will end up with

two (or
more) files with the same name, which is a programmer

error.

The geom gp has to have a start method defined.

The topology lock has to be held.

g_destroy_provider():

The provider must not have consumers attached.

The access count has to be 0.

The topology lock has to be held.

RETURN VALUES

The g_new_providerf() function returns a pointer to the new

ly created
provider.

EXAMPLES

Create an example provider, set its parameters and make it

usable.

struct g_provider *
create_example_provider(struct g_geom *gp)
{

struct g_provider *pp;

g_topology_lock();
pp = g_new_providerf(gp, "example_provider");
g_topology_unlock();
pp->mediasize = 65536;
pp->sectorsize = 512;
g_error_provider(pp, 0);

return (pp);

}

SEE ALSO

geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9),

g_bio(9),
g_consumer(9), g_data(9), g_event(9), g_geom(9),

g_provider_by_name(9),
g_wither_geom(9)

AUTHORS

This manual page was written by Pawel Jakub Dawidek

<pjd@FreeBSD.org>.

BSD January 16, 2004

BSD