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

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.Dd January 16, 2004
.Dt g_provider 9
.Os
.Sh NAME
.Nm g_new_providerf ,
.Nm g_destroy_provider ,
.Nm g_error_provider
.Nd "GEOM providers management"
.Sh SYNOPSIS
.In geom/geom.h
.Ft "struct g_provider *"
.Fn g_new_providerf "struct g_geom *gp" "const char *fmt" ...
.Ft void
.Fn g_destroy_provider "struct g_provider *pp"
.Ft void
.Fn g_error_provider "struct g_provider *pp" "int error"
.Sh DESCRIPTION
The GEOM provider is the front gate at which a geom offers service.
A provider is
.Dq a disk\-like thing which appears in Pa /dev
\- a logical disk in other words.
All providers have three main properties: name, sectorsize and size.
.Pp
The
.Fn g_new_providerf
function creates a new provider and attaches it to geom
.Fa gp .
The provider name is created in a printf\-like way from the rest of
the arguments.
After creation, the provider is unusable, because
.Fn g_new_providerf
sets its error to
.Er ENXIO .
The function
.Fn g_error_provider
should be used to reset this error, but before it is called, two
fields should be set in the provider structure:
.Va mediasize
and
.Va sectorsize
as well as other initialization things should be done first.
.Pp
The
.Fn g_destroy_provider
function destroys the given provider, cancels all related pending events and
removes corresponding devfs entry.
.Pp
The
.Fn g_error_provider
function is used to set a provider error value.
If it set to a nonzero value, all I/O requests will be denied,
increasing its access count will not be possible (error
.Fa error
will be returned).
.Sh RESTRICTIONS/CONDITIONS
.Fn g_new_provider :
.Bl -item -offset indent
.It
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 programmer error.
.It
The geom related to the created provider must have
.Fa start
field defined.
.It
The topology lock has to be held.
.El
.Pp
.Fn g_destroy_provider :
.Bl -item -offset indent
.It
No consumers have to be attached.
.It
The access count has to be 0.
.It
The topology lock has to be held.
.El
.Sh RETURN VALUES
.Fn g_new_providerf
returns a pointer to the newly created provider.
.Sh EXAMPLES
Create an example provider, set its parameters and make it usable.
.Bd -literal -offset indent
struct g_provider *
create_example_provider(struct g_geom *gp)
{
	struct g_provider *pp;

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

	return (pp);
}
.Ed
.Sh SEE ALSO
.Xr DECLARE_GEOM_CLASS 9 ,
.Xr geom 4 ,
.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_geom 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 .