259 lines
7.1 KiB
Groff
259 lines
7.1 KiB
Groff
.\" Copyright (c) 2003 Poul-Henning Kamp
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The names of the authors may not be used to endorse or promote
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.\" products derived from this software without specific prior written
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.\" permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 7, 2004
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.Dt LIBGEOM 3
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.Os
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.Sh NAME
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.Nm geom_stats_open ,
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.Nm geom_stats_close ,
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.Nm geom_stats_resync ,
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.Nm geom_stats_snapshot_get ,
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.Nm geom_stats_snapshot_free ,
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.Nm geom_stats_snapshot_timestamp ,
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.Nm geom_stats_snapshot_reset ,
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.Nm geom_stats_snapshot_next ,
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.Nm gctl_get_handle ,
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.Nm gctl_ro_param ,
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.Nm gctl_rw_param ,
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.Nm gctl_issue ,
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.Nm gctl_free ,
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.Nm gctl_dump
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.Nd userland API library for kernel GEOM subsystem
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.Sh LIBRARY
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.Lb libgeom
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.Sh SYNOPSIS
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.In libgeom.h
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.Ss "Statistics Functions"
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.Ft void
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.Fn geom_stats_close void
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.Ft int
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.Fn geom_stats_open void
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.Ft void
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.Fn geom_stats_resync void
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.Ft "void *"
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.Fn geom_stats_snapshot_get void
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.Ft void
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.Fn geom_stats_snapshot_free "void *arg"
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.Ft void
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.Fn geom_stats_snapshot_timestamp "void *arg" "struct timespec *tp"
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.Ft void
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.Fn geom_stats_snapshot_reset "void *arg"
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.Ft "struct g_stat *"
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.Fn geom_stats_snapshot_next "void *arg"
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.Ss "Control Functions"
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.Ft "struct gctl_req *"
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.Fn gctl_get_handle "void"
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.Ft void
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.Fn gctl_ro_param "struct gctl_req *req" "const char *name" "int len" "const void *value"
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.Ft void
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.Fn gctl_rw_param "struct gctl_req *req" "const char *name" "int len" "void *value"
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.Ft "const char *"
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.Fn gctl_issue "struct gctl_req *req"
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.Ft void
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.Fn gctl_free "struct gctl_req *req"
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.Ft void
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.Fn gctl_dump "struct gctl_req *req" "FILE *f"
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.Sh DESCRIPTION
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The
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.Nm geom
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library contains the official and publicized API for
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interacting with the GEOM subsystem in the kernel.
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.Ss "Statistics Functions"
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GEOM collects statistics data for all consumers and providers, but does
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not perform any normalization or presentation on the raw data, this is
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left as an excercize for user-land presentation utilities.
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.Pp
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The
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.Fn geom_stats_open
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and
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.Fn geom_stats_close
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functions open and close the necessary pathways to access the raw
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statistics information in the kernel.
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These functions are likely to
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open one or more files and cache the file descriptors locally.
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The
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.Fn geom_stats_open
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function returns zero on success, and sets
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.Va errno
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if not.
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.Pp
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The
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.Fn geom_stats_resync
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function will check if more statistics collection points have been
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added in the kernel since
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.Fn geom_stats_open
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or the previous call to
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.Fn geom_stats_resync .
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.Pp
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The
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.Fn geom_stats_snapshot_get
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function
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will acquire a snapshot of the raw data from the kernel, and while a
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reasonable effort is made to make this snapshot as atomic and consistent
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as possible, no guarantee is given that it will actually be so.
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The snapshot must be freed again using the
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.Fn geom_stats_snapshot_free
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function.
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The
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.Fn geom_stats_snapshot_get
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function returns
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.Dv NULL
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on failure.
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.Pp
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The
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.Fn geom_stats_snapshot_timestamp
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function
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provides access to the timestamp acquired in the snapshot.
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.Pp
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The
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.Fn geom_stats_snapshot_reset
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and
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.Fn geom_stats_snapshot_next
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functions
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provide an iterator over the statistics slots in the snapshot.
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The
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.Fn geom_stats_snapshot_reset
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function
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forces the internal pointer in the snapshot back to before the first item.
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The
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.Fn geom_stats_snapshot_next
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function
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returns the next item, and
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.Dv NULL
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if there are no more items in the snapshot.
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.Ss "Control Functions"
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The
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.Fn gctl_*
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functions are used to send requests to GEOM classes.
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In order for a GEOM
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class to actually be able to receive these requests, it must have defined a
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"ctlreq" method.
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.Pp
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A
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.Vt "struct gctl_req *" ,
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obtained with
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.Fn gctl_get_handle ,
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can hold any number of parameters, which must be added to it with
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.Fn gctl_ro_param
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(for read-only parameters) or
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.Fn gctl_rw_param
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(for read/write parameters).
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.Pp
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Both
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.Fn gctl_ro_param
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and
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.Fn gctl_rw_param
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take a string
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.Fa name ,
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which is used to identify the parameter, and a
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.Fa value ,
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which contains, in the read-only case, the data to be passed to the
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GEOM class, or, in the read/write case, a pointer to preallocated memory
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that the GEOM class should fill with the desired data.
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If
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.Fa len
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is negative, it is assumed that
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.Fa value
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is an
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.Tn ASCII
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string and the actual length is taken from the string length of
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.Fa value ;
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otherwise it must hold the size of
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.Fa value .
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.Pp
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A parameter with a
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.Fa name
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containing the string
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.Qq Li class
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is mandatory for each request, and the
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corresponding
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.Fa value
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must hold the name of the GEOM class where the request should be sent to.
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.Pp
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Also mandatory for each request is a parameter with a
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.Fa name
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called
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.Qq Li verb ,
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and the corresponding
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.Fa value
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needs to hold the command string that the GEOM class should react upon.
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.Pp
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Once all desired parameters are filled in, the request must be sent to
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the GEOM subsystem with
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.Fn gctl_issue ,
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which returns
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.Dv NULL
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on success, or a string containing the error message
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on failure.
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.Pp
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After the request is finished, the allocated memory should be released with
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.Fn gctl_free .
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.Pp
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The
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.Fn gctl_dump
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function
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can be used to format the contents of
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.Fa req
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to the open file handle pointed to by
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.Fa f ,
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for debugging purposes.
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.Pp
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Error handling for the control functions is postponed until the call
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to
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.Fn gctl_issue ,
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which returns
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.Dv NULL
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on success, or an error message corresponding to the
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first error which happened.
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.Sh EXAMPLES
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Create a request that is to be sent to the CCD class, and tell
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it to destroy a specific geom:
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.Bd -literal -offset indent
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H = gctl_get_handle();
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gctl_ro_param(H, "verb", -1, "destroy geom");
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gctl_ro_param(H, "class", -1, "CCD");
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sprintf(buf, "ccd%d", ccd);
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gctl_ro_param(H, "geom", -1, buf);
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errstr = gctl_issue(H);
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if (errstr != NULL)
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err(1, "could not destroy ccd: %s", errstr);
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gctl_free(H);
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.Ed
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.Sh SEE ALSO
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.Pa http://ezine.daemonnews.org/200308/blueprints.html
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.Sh HISTORY
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The
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.Nm geom
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library appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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.An Poul-Henning Kamp Aq phk@FreeBSD.org
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.An Lukas Ertl Aq le@FreeBSD.org
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