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

.\"
.\" Copyright (c) 2004-2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd January 16, 2004
.Dt G_DATA 9
.Os
.Sh NAME
.Nm g_read_data ,
.Nm g_write_data
.Nd "read/write data from/to GEOM consumer"
.Sh SYNOPSIS
.In geom/geom.h
.Ft "void *"
.Fo g_read_data
.Fa "struct g_consumer *cp" "off_t offset" "off_t length" "int *error"
.Fc
.Ft int
.Fo g_write_data
.Fa "struct g_consumer *cp" "off_t offset" "void *ptr" "off_t length"
.Fc
.Sh DESCRIPTION
The
.Fn g_read_data
function reads
.Fa length
bytes of data from the provider attached to consumer
.Fa cp ,
starting at offset
.Fa offset .
The buffer returned from
.Fn g_read_data
is allocated with
.Fn g_malloc ,
so it should be freed by the caller with
.Fn g_free
after use.
If the operation fails, an error value will be stored in the
.Fa error
argument if it is not
.Dv NULL .
.Pp
The
.Fn g_write_data
function writes
.Fa length
bytes of data from the buffer pointed to by
.Fa ptr
to the provider attached to consumer
.Fa cp ,
starting at offset
.Fa offset .
.Sh RESTRICTIONS/CONDITIONS
The
.Fa length
argument
should be a multiple of the provider's sectorsize
and less than or equal to
.Dv DFLTPHYS
.Dv ( DFLTPHYS
is defined in
.In sys/param.h ) .
.Pp
The topology lock must not be held.
.Sh RETURN VALUES
The
.Fn g_read_data
function returns a pointer to a data buffer or
.Dv NULL
if an error occurred.
In that case an error value is stored in the
.Fa error
argument unless it is
.Dv NULL .
.Pp
The
.Fn g_write_data
function returns 0 if successful; otherwise an error code is returned.
.Sh ERRORS
Possible errors:
.Bl -tag -width Er
.It Bq Er EIO
An I/O error occurred while reading from or writing to the consumer.
.El
.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_event 9 ,
.Xr g_geom 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 .