458 lines
13 KiB
Groff
458 lines
13 KiB
Groff
.\" Copyright (c) 1996
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.\" Julian Elischer <julian@FreeBSD.org>. 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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.\"
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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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.\"
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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 February 8, 2012
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.Dt CD 4
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.Os
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.Sh NAME
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.Nm cd
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.Nd SCSI CD-ROM driver
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.Sh SYNOPSIS
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.Cd device cd
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.Cd "options ""CHANGER_MIN_BUSY_SECONDS=3"""
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.Cd "options ""CHANGER_MAX_BUSY_SECONDS=11"""
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for a
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.Tn SCSI
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.Tn CD-ROM
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(Compact Disc-Read Only Memory) drive.
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In an attempt to look like a regular disk, the
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.Nm
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driver synthesizes a partition table, with one partition covering the entire
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.Tn CD-ROM .
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It is possible to modify this partition table using
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.Xr disklabel 8 ,
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but it will only last until the
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.Tn CD-ROM
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is unmounted.
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In general the interfaces are similar to those described by
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.Xr ada 4
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and
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.Xr da 4 .
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.Pp
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As the
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.Tn SCSI
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adapter is probed during boot, the
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.Tn SCSI
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bus is scanned for devices.
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Any devices found which answer as CDROM
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(type 5) or WORM (type 4) type devices will be `attached' to the
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.Nm
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driver.
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Prior to
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.Fx 2.1 ,
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the first device found will be attached as
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.Li cd0
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the next,
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.Li cd1 ,
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etc.
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Beginning in
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.Fx 2.1
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it is possible to specify what cd unit a device should
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come on line as; refer to
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.Xr scsi 4
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for details on kernel configuration.
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.Pp
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The system utility
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.Xr disklabel 8
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may be used to read the synthesized
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disk label
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structure, which will contain correct figures for the size of the
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.Tn CD-ROM
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should that information be required.
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.Sh KERNEL CONFIGURATION
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Any number of
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.Tn CD-ROM
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devices may be attached to the system regardless of system
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configuration as all resources are dynamically allocated.
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.Sh IOCTLS
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The following
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.Xr ioctl 2
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calls which apply to
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.Tn SCSI
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.Tn CD-ROM
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drives are defined
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in the header files
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.In sys/cdio.h
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and
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.In sys/disklabel.h .
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.Bl -tag -width CDIOCREADSUBCHANNEL
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.It Dv DIOCGDINFO
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.It Dv DIOCSDINFO
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.Pq Li "struct disklabel"
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Read or write the in-core copy of the disklabel for the
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drive.
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The disklabel is initialized with information
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read from the scsi inquiry commands, and should be the same as
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the information printed at boot.
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This structure is defined in the header file
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.In sys/disklabel.h .
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.It Dv CDIOCPLAYTRACKS
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.Pq Li "struct ioc_play_track"
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Start audio playback given a track address and length.
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The structure is defined as follows:
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.Bd -literal -offset indent
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struct ioc_play_track
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{
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u_char start_track;
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u_char start_index;
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u_char end_track;
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u_char end_index;
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};
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.Ed
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.It Dv CDIOCPLAYBLOCKS
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.Pq Li "struct ioc_play_blocks"
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Start audio playback given a block address and length.
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The structure is defined as follows:
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.Bd -literal -offset indent
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struct ioc_play_blocks
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{
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int blk;
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int len;
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};
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.Ed
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.It Dv CDIOCPLAYMSF
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.Pq Li "struct ioc_play_msf"
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Start audio playback given a `minutes-seconds-frames' address and
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length.
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The structure is defined as follows:
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.Bd -literal -offset indent
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struct ioc_play_msf
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{
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u_char start_m;
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u_char start_s;
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u_char start_f;
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u_char end_m;
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u_char end_s;
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u_char end_f;
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};
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.Ed
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.It Dv CDIOCREADSUBCHANNEL
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.Pq Li "struct ioc_read_subchannel"
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Read information from the subchannel at the location specified by this
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structure:
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.Bd -literal -offset indent
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struct ioc_read_subchannel {
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u_char address_format;
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#define CD_LBA_FORMAT 1
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#define CD_MSF_FORMAT 2
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u_char data_format;
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#define CD_SUBQ_DATA 0
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#define CD_CURRENT_POSITION 1
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#define CD_MEDIA_CATALOG 2
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#define CD_TRACK_INFO 3
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u_char track;
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int data_len;
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struct cd_sub_channel_info *data;
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};
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.Ed
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.It Dv CDIOREADTOCHEADER
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.Pq Li "struct ioc_toc_header"
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Return summary information about the table of contents for the mounted
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.Tn CD-ROM .
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The information is returned into the following structure:
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.Bd -literal -offset indent
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struct ioc_toc_header {
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u_short len;
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u_char starting_track;
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u_char ending_track;
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};
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.Ed
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.It Dv CDIOREADTOCENTRYS
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.Pq Li "struct ioc_read_toc_entry"
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Return information from the table of contents entries mentioned.
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.Pq Yes, this command name is misspelled.
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The argument structure is defined as follows:
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.Bd -literal -offset indent
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struct ioc_read_toc_entry {
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u_char address_format;
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u_char starting_track;
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u_short data_len;
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struct cd_toc_entry *data;
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};
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.Ed
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The requested data is written into an area of size
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.Li data_len
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and pointed to by
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.Li data .
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.It Dv CDIOCSETPATCH
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.Pq Li "struct ioc_patch"
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Attach various audio channels to various output channels.
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The argument structure is defined thusly:
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.Bd -literal -offset indent
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struct ioc_patch {
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u_char patch[4];
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/* one for each channel */
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};
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.Ed
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.It Dv CDIOCGETVOL
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.It Dv CDIOCSETVOL
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.Pq Li "struct ioc_vol"
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Get (set) information about the volume settings of the output channels.
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The argument structure is as follows:
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.Bd -literal -offset indent
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struct ioc_vol
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{
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u_char vol[4];
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/* one for each channel */
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};
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.Ed
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.It Dv CDIOCSETMONO
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Patch all output channels to all source channels.
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.It Dv CDIOCSETSTEREO
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Patch left source channel to the left output channel and the right
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source channel to the right output channel.
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.It Dv CDIOCSETMUTE
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Mute output without changing the volume settings.
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.It Dv CDIOCSETLEFT
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.It Dv CDIOCSETRIGHT
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Attach both output channels to the left (right) source channel.
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.It Dv CDIOCSETDEBUG
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.It Dv CDIOCCLRDEBUG
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Turn on (off) debugging for the appropriate device.
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.It Dv CDIOCPAUSE
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.It Dv CDIOCRESUME
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Pause (resume) audio play, without resetting the location of the read-head.
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.It Dv CDIOCRESET
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Reset the drive.
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.It Dv CDIOCSTART
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.It Dv CDIOCSTOP
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Tell the drive to spin-up (-down) the
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.Tn CD-ROM .
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.It Dv CDIOCALLOW
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.It Dv CDIOCPREVENT
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Tell the drive to allow (prevent) manual ejection of the
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.Tn CD-ROM
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disc.
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Not all drives support this feature.
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.It Dv CDIOCEJECT
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Eject the
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.Tn CD-ROM .
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.It Dv CDIOCCLOSE
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Tell the drive to close its door and load the media.
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Not all drives support this feature.
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.El
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.Sh NOTES
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When a
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.Tn CD-ROM
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is changed in a drive controlled by the
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.Nm
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driver, then the act of changing the media will invalidate the
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disklabel and information held within the kernel.
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To stop corruption,
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all accesses to the device will be discarded until there are no more
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open file descriptors referencing the device.
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During this period, all
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new open attempts will be rejected.
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When no more open file descriptors
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reference the device, the first next open will load a new set of
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parameters (including disklabel) for the drive.
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.Pp
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The audio code in the
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.Nm
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driver only support
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.Tn SCSI-2
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standard audio commands.
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As many
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.Tn CD-ROM
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manufacturers have not followed the standard, there are many
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.Tn CD-ROM
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drives for which audio will not work.
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Some work is planned to support
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some of the more common `broken'
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.Tn CD-ROM
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drives; however, this is not yet under way.
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.Sh CHANGER OPERATION
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This driver has built-in support for LUN-based CD changers.
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A LUN-based CD
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changer is a drive that can hold two or more CDs, but only has one CD
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player mechanism.
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Each CD in the drive shows up as a separate logical unit
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on the
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.Tn SCSI
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bus.
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The
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.Nm
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driver automatically recognizes LUN-based changers, and routes commands for
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changers through an internal scheduler.
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The scheduler prevents changer
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"thrashing", which is caused by sending commands to different LUNs in the
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changer at the same time.
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.Pp
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The scheduler honors minimum and maximum time
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quanta that the driver will spend on a particular LUN.
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The minimum time
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is the guaranteed minimum amount of time that the driver will spend on a
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given LUN, even if there is no outstanding I/O for that LUN.
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The maximum
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time is the maximum amount of time the changer will spend on a LUN if there
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is outstanding I/O for another LUN.
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If there is no outstanding I/O for
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another LUN, the driver will allow indefinite access to a given LUN.
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.Pp
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The minimum and maximum time quanta are configurable via kernel options and
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also via sysctl and kernel tunable variables.
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The kernel options are:
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.Pp
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.Bl -item -compact
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.It
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.Cd "options ""CHANGER_MIN_BUSY_SECONDS=3"""
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.It
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.Cd "options ""CHANGER_MAX_BUSY_SECONDS=11"""
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.El
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.Pp
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The sysctl/kernel tunable variables are:
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.Pp
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.Bl -item -compact
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.It
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.Va kern.cam.cd.changer.min_busy_seconds
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.It
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.Va kern.cam.cd.changer.max_busy_seconds
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.El
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.Pp
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It is suggested that the user try experimenting with the minimum and
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maximum timeouts via the sysctl variables to arrive at the proper values
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for your changer.
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Once you have settled on the proper timeouts for your
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changer, you can then put them in your kernel config file.
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.Pp
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If your system does have a LUN-based changer, you may notice that the
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probe messages for the various LUNs of the changer will continue to appear
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while the boot process is going on.
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This is normal, and is caused by the
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changer scheduling code.
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.Sh SYSCTL VARIABLES
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The following variables are available as both
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.Xr sysctl 8
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variables and
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.Xr loader 8
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tunables:
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.Bl -tag -width 12
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.It kern.cam.cd.retry_count
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.Pp
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This variable determines how many times the
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.Nm
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driver will retry a READ or WRITE command.
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This does not affect the number of retries used during probe time or for
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the
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.Nm
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driver dump routine.
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This value currently defaults to 4.
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.It kern.cam.cd.%d.minimum_cmd_size
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.Pp
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The
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.Nm
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driver attempts to automatically determine whether the drive it is talking
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to supports 6 byte or 10 byte MODE SENSE/MODE SELECT operations.
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Many
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.Tn SCSI
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drives only support 6 byte commands, and
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.Tn ATAPI
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drives only support 10 byte commands.
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The
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.Nm
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driver first attempts to determine whether the protocol in use typically
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supports 6 byte commands by issuing a CAM Path Inquiry CCB.
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It will then default to 6 byte or 10 byte commands as appropriate.
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After that, the
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.Nm
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driver defaults to using 6 byte commands (assuming the protocol the drive
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speaks claims to support 6 byte commands), until one fails with a
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.Tn SCSI
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ILLEGAL REQUEST error.
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Then it tries the 10 byte version of the command to
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see if that works instead.
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Users can change the default via per-drive
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sysctl variables and loader tunables.
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Where
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.Dq %d
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is the unit number of the drive in question.
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Valid minimum command sizes
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are 6 and 10.
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Any value above 6 will be rounded to 10, and any value below
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6 will be rounded to 6.
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.It kern.cam.cd.changer.min_busy_seconds
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.It kern.cam.cd.changer.max_busy_seconds
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.Pp
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Tune how long individual LUNs are 'locked' for I/O operations to
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optimize changer operation.
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See CHANGER OPERATION section for information on how to use these items.
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.El
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.Sh FILES
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.Bl -tag -width /dev/cd[0-9][a-h] -compact
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.It Pa /dev/cd[0-9][a-h]
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raw mode
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.Tn CD-ROM
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devices
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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.Xr cam 4 ,
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.Xr da 4 ,
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.Xr disklabel 8 ,
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.Xr cd 9
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.Sh HISTORY
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This
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.Nm
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driver is based upon the
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.Nm
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driver written by Julian Elischer, which appeared in
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.Bx 386 0.1 .
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The
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CAM version of the
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.Nm
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driver was written by Kenneth Merry and first appeared in
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.Fx 3.0 .
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.Sh BUGS
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The names of the structures used for the third argument to
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.Fn ioctl
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were poorly chosen, and a number of spelling errors have survived in
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the names of the
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.Fn ioctl
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commands.
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.Pp
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There is no mechanism currently to set different minimum and maximum
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timeouts for different CD changers; the timeout values set by the kernel
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options or the sysctl variables apply to all LUN-based CD changers in the
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system.
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It is possible to implement such support, but the sysctl
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implementation at least would be rather inelegant, because of the current
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inability of the sysctl code to handle the addition of nodes after compile
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time.
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Thus, it would take one dynamically sized sysctl variable and a
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userland utility to get/set the timeout values.
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Implementation of separate
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timeouts for different CD devices in the kernel config file would likely
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require modification of
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.Xr config 8
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to support the two timeouts when hardwiring
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.Nm
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devices.
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