1.\" 2.\" Copyright (c) 2004-2005 Pawel Jakub Dawidek <pjd@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 15.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 18.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.Dd March 30, 2020 26.Dt G_DATA 9 27.Os 28.Sh NAME 29.Nm g_read_data , 30.Nm g_write_data 31.Nd "read/write data from/to GEOM consumer" 32.Sh SYNOPSIS 33.In geom/geom.h 34.Ft "void *" 35.Fo g_read_data 36.Fa "struct g_consumer *cp" "off_t offset" "off_t length" "int *error" 37.Fc 38.Ft int 39.Fo g_write_data 40.Fa "struct g_consumer *cp" "off_t offset" "void *ptr" "off_t length" 41.Fc 42.Sh DESCRIPTION 43The 44.Fn g_read_data 45function reads 46.Fa length 47bytes of data from the provider attached to consumer 48.Fa cp , 49starting at offset 50.Fa offset . 51The buffer returned from 52.Fn g_read_data 53is allocated with 54.Fn g_malloc , 55so it should be freed by the caller with 56.Fn g_free 57after use. 58If the operation fails, an error value will be stored in the 59.Fa error 60argument if it is not 61.Dv NULL . 62.Pp 63The 64.Fn g_write_data 65function writes 66.Fa length 67bytes of data from the buffer pointed to by 68.Fa ptr 69to the provider attached to consumer 70.Fa cp , 71starting at offset 72.Fa offset . 73.Sh RESTRICTIONS/CONDITIONS 74The 75.Fa length 76argument 77should be a multiple of the provider's sectorsize 78and less than or equal to 79.Dv DFLTPHYS 80.Dv ( DFLTPHYS 81is defined in 82.In sys/param.h ) . 83.Pp 84The topology lock must not be held. 85.Sh RETURN VALUES 86The 87.Fn g_read_data 88function returns a pointer to a data buffer or 89.Dv NULL 90if an error occurred. 91In that case an error value is stored in the 92.Fa error 93argument unless it is 94.Dv NULL . 95.Pp 96The 97.Fn g_write_data 98function returns 0 if successful; otherwise an error code is returned. 99.Sh ERRORS 100Possible errors: 101.Bl -tag -width Er 102.It Bq Er EIO 103An I/O error occurred while reading from or writing to the consumer. 104.It Bq Er EINTEGRITY 105Corrupted data was detected while reading from the consumer. 106.El 107.Sh SEE ALSO 108.Xr geom 4 , 109.Xr DECLARE_GEOM_CLASS 9 , 110.Xr g_access 9 , 111.Xr g_attach 9 , 112.Xr g_bio 9 , 113.Xr g_consumer 9 , 114.Xr g_event 9 , 115.Xr g_geom 9 , 116.Xr g_provider 9 , 117.Xr g_provider_by_name 9 , 118.Xr g_wither_geom 9 119.Sh AUTHORS 120.An -nosplit 121This manual page was written by 122.An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org . 123