.\" Copyright (c) 1996 .\" Julian Elischer . 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 AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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: src/share/man/man4/cd.4,v 1.17.2.8 2003/06/03 14:32:09 hmp Exp $ .\" .Dd February 18, 2019 .Dt CD 4 .Os .Sh NAME .Nm cd .Nd SCSI CD-ROM driver .Sh SYNOPSIS .Cd device cd .Cd device cd1 at scbus0 target 4 unit 0 .Cd "options CHANGER_MIN_BUSY_SECONDS=3" .Cd "options CHANGER_MAX_BUSY_SECONDS=11" .Sh DESCRIPTION The .Nm driver provides support for a .Tn SCSI .Tn CD-ROM (Compact Disc-Read Only Memory) drive. In an attempt to look like a regular disk, the .Nm driver synthesizes a partition table, with one partition covering the entire .Tn CD-ROM . It is possible to modify this partition table using .Xr disklabel 8 , but it will only last until the .Tn CD-ROM is unmounted. In general the interfaces are similar to those described by .Xr ad 4 and .Xr da 4 . .Pp As the .Tn SCSI adapter is probed during boot, the .Tn SCSI bus is scanned for devices. Any devices found which answer as CDROM (type 5) or WORM (type 4) type devices will be `attached' to the .Nm driver. Prior to .Fx 2.1 , the first device found will be attached as .Li cd0 the next, .Li cd1 , etc. Beginning in .Fx 2.1 it is possible to specify what cd unit a device should come on line as; refer to .Xr scsi 4 for details on kernel configuration. .Pp The .Cd target string is followed by the device's standard .Tn SCSI device ID number. The .Cd unit string is followed by the Logical Unit Number .Pq Tn LUN of the .Tn SCSI device's sub-device, if any, or zero. .Pp The system utility .Xr disklabel 8 may be used to read the synthesized disk label structure, which will contain correct figures for the size of the .Tn CD-ROM should that information be required. .Sh IOCTLS The following .Xr ioctl 2 calls which apply to .Tn SCSI .Tn CD-ROM drives are defined in the header files .In sys/cdio.h and .In sys/disklabel.h . .Bl -tag -width ".Dv CDIOCREADSUBCHANNEL" .It Dv DIOCGDINFO .It Dv DIOCSDINFO .Pq Li "struct disklabel" Read or write the in-core copy of the disklabel for the drive. The disklabel is initialized with information read from the scsi inquiry commands, and should be the same as the information printed at boot. This structure is defined in .Xr disklabel 5 . .It Dv CDIOCPLAYTRACKS .Pq Li "struct ioc_play_track" Start audio playback given a track address and length. The structure is defined as follows: .Bd -literal -offset indent struct ioc_play_track { u_char start_track; u_char start_index; u_char end_track; u_char end_index; }; .Ed .It Dv CDIOCPLAYBLOCKS .Pq Li "struct ioc_play_blocks" Start audio playback given a block address and length. The structure is defined as follows: .Bd -literal -offset indent struct ioc_play_blocks { int blk; int len; }; .Ed .It Dv CDIOCPLAYMSF .Pq Li "struct ioc_play_msf" Start audio playback given a `minutes-seconds-frames' address and length. The structure is defined as follows: .Bd -literal -offset indent struct ioc_play_msf { u_char start_m; u_char start_s; u_char start_f; u_char end_m; u_char end_s; u_char end_f; }; .Ed .It Dv CDIOCREADSUBCHANNEL .Pq Li "struct ioc_read_subchannel" Read information from the subchannel at the location specified by this structure: .Bd -literal -offset indent struct ioc_read_subchannel { u_char address_format; #define CD_LBA_FORMAT 1 #define CD_MSF_FORMAT 2 u_char data_format; #define CD_SUBQ_DATA 0 #define CD_CURRENT_POSITION 1 #define CD_MEDIA_CATALOG 2 #define CD_TRACK_INFO 3 u_char track; int data_len; struct cd_sub_channel_info *data; }; .Ed .It Dv CDIOREADTOCHEADER .Pq Li "struct ioc_toc_header" Return summary information about the table of contents for the mounted .Tn CD-ROM . The information is returned into the following structure: .Bd -literal -offset indent struct ioc_toc_header { u_short len; u_char starting_track; u_char ending_track; }; .Ed .It Dv CDIOREADTOCENTRYS .Pq Li "struct ioc_read_toc_entry" Return information from the table of contents entries mentioned. .Pq Yes, this command name is misspelled. The argument structure is defined as follows: .Bd -literal -offset indent struct ioc_read_toc_entry { u_char address_format; u_char starting_track; u_short data_len; struct cd_toc_entry *data; }; .Ed The requested data is written into an area of size .Li data_len and pointed to by .Li data . .It Dv CDIOCSETPATCH .Pq Li "struct ioc_patch" Attach various audio channels to various output channels. The argument structure is defined thusly: .Bd -literal -offset indent struct ioc_patch { u_char patch[4]; /* one for each channel */ }; .Ed .It Dv CDIOCGETVOL .It Dv CDIOCSETVOL .Pq Li "struct ioc_vol" Get (set) information about the volume settings of the output channels. The argument structure is as follows: .Bd -literal -offset indent struct ioc_vol { u_char vol[4]; /* one for each channel */ }; .Ed .It Dv CDIOCSETMONO Patch all output channels to all source channels. .It Dv CDIOCSETSTEREO Patch left source channel to the left output channel and the right source channel to the right output channel. .It Dv CDIOCSETMUTE Mute output without changing the volume settings. .It Dv CDIOCSETLEFT .It Dv CDIOCSETRIGHT Attach both output channels to the left (right) source channel. .It Dv CDIOCSETDEBUG .It Dv CDIOCCLRDEBUG Turn on (off) debugging for the appropriate device. .It Dv CDIOCPAUSE .It Dv CDIOCRESUME Pause (resume) audio play, without resetting the location of the read-head. .It Dv CDIOCRESET Reset the drive. .It Dv CDIOCSTART .It Dv CDIOCSTOP Tell the drive to spin-up (-down) the .Tn CD-ROM . .It Dv CDIOCALLOW .It Dv CDIOCPREVENT Tell the drive to allow (prevent) manual ejection of the .Tn CD-ROM disc. Not all drives support this feature. .It Dv CDIOCEJECT Eject the .Tn CD-ROM . .It Dv CDIOCCLOSE Tell the drive to close its door and load the media. Not all drives support this feature. .El .Sh NOTES When a .Tn CD-ROM is changed in a drive controlled by the .Nm driver, then the act of changing the media will invalidate the disklabel and information held within the kernel. To stop corruption, all accesses to the device will be discarded until there are no more open file descriptors referencing the device. During this period, all new open attempts will be rejected. When no more open file descriptors reference the device, the first next open will load a new set of parameters (including disklabel) for the drive. .Pp The audio code in the .Nm driver only support .Tn SCSI-2 standard audio commands. Because many .Tn CD-ROM manufacturers have not followed the standard, there are many .Tn CD-ROM drives for which audio will not work. Some work is planned to support some of the more common `broken' .Tn CD-ROM drives; however, this is not yet under way. .Sh CHANGER OPERATION This driver has built-in support for LUN-based CD changers. A LUN-based CD changer is a drive that can hold two or more CDs, but only has one CD player mechanism. Each CD in the drive shows up as a separate logical unit on the .Tn SCSI bus. The .Nm driver automatically recognizes LUN-based changers, and routes commands for changers through an internal scheduler. The scheduler prevents changer "thrashing", which is caused by sending commands to different LUNs in the changer at the same time. .Pp The scheduler honors minimum and maximum time quanta that the driver will spend on a particular LUN. The minimum time is the guaranteed minimum amount of time that the driver will spend on a given LUN, even if there is no outstanding I/O for that LUN. The maximum time is the maximum amount of time the changer will spend on a LUN if there is outstanding I/O for another LUN. If there is no outstanding I/O for another LUN, the driver will allow indefinite access to a given LUN. .Pp The minimum and maximum time quanta are configurable via kernel options and also via sysctl variables. The kernel options are: .Pp .Bl -item -compact .It .Cd "options ""CHANGER_MIN_BUSY_SECONDS=3""" .It .Cd "options ""CHANGER_MAX_BUSY_SECONDS=11""" .El .Pp The sysctl variables are: .Pp .Bl -item -compact .It .Va kern.cam.cd.changer.min_busy_seconds .It .Va kern.cam.cd.changer.max_busy_seconds .El .Pp It is suggested that the user try experimenting with the minimum and maximum timeouts via the sysctl variables to arrive at the proper values for your changer. Once you have settled on the proper timeouts for your changer, you can then put them in your kernel config file. .Pp If your system does have a LUN-based changer, you may notice that the probe messages for the various LUNs of the changer will continue to appear while the boot process is going on. This is normal, and is caused by the changer scheduling code. .Sh FILES .Bl -tag -width /dev/cd[0-9][a-h] -compact .It Pa /dev/cd[0-9][a-h] raw mode .Tn CD-ROM devices .El .Sh DIAGNOSTICS None. .Sh SEE ALSO .Xr da 4 , .Xr scsi 4 , .Xr disklabel 5 , .Xr disklabel 8 , .Xr cd 9 .Sh HISTORY This .Nm driver is based upon the .Nm driver written by Julian Elischer, which appeared in .Bx 386 0.1 . The CAM version of the .Nm driver was written by Kenneth Merry and first appeared in .Fx 3.0 . .Sh BUGS The names of the structures used for the third argument to .Fn ioctl were poorly chosen, and a number of spelling errors have survived in the names of the .Fn ioctl commands. .Pp There is no mechanism currently to set different minimum and maximum timeouts for different CD changers; the timeout values set by the kernel options or the sysctl variables apply to all LUN-based CD changers in the system. It is possible to implement such support, but the sysctl implementation at least would be rather inelegant, because of the current inability of the sysctl code to handle the addition of nodes after compile time. Thus, it would take one dynamically sized sysctl variable and a userland utility to get/set the timeout values. Implementation of separate timeouts for different CD devices in the kernel config file would likely require modification of .Xr config 8 to support the two timeouts when hardwiring .Nm devices.