CD(4)

NAME
cd - SCSI CD-ROM driver

SYNOPSIS
device cd
device cd1 at scbus0 target 4 lun 0

DESCRIPTION
The cd driver provides support for a SCSI CD-ROM (Compact Disc-Read Only Memory) drive. In an attempt to look like a regular disk, the cd driver synthesizes a partition table, with one partition covering the entire CD-ROM. It is possible to modify this partition table using disklabel(8), but it will only last until the CD-ROM is unmounted. In general the interfaces are similar to those described by wd(4) and sd(4).

As the SCSI adapter is probed during boot, the SCSI bus is scanned for devices. Any devices found which answer as `Read-only' type devices will be `attached' to the cd driver. In FreeBSD releases prior to 2.1, the first found will be attached as cd0 the next, cd1, etc. Beginning in 2.1 it is possible to specify what cd unit a device should come on line as; refer to scsi(4) for details on kernel configuration.

The system utility disklabel(8) may be used to read the synthesized disk label structure, which will contain correct figures for the size of the CD-ROM should that information be required.

KERNEL CONFIGURATION
Any number of CD-ROM devices may be attached to the system regardless of system configuration as all resources are dynamically allocated.

IOCTLS
The following ioctl(2) calls which apply to SCSI CD-ROM drives are defined in the header files <sys/cdio.h> and <sys/disklabel.h>.

DIOCGDINFO
DIOCSDINFO
    (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 disklabel(5).
CDIOCCAPABILITY
    (struct ioc_capability) Retrieve information from the drive on what features it supports. The information is returned in the following structure:

        struct ioc_capability {
        	u_long	play_function;
        #define CDDOPLAYTRK	0x00000001
        	/* Can play tracks/index */
        #define	CDDOPLAYMSF	0x00000002
        	/* Can play msf to msf */
        #define	CDDOPLAYBLOCKS	0x00000004
        	/* Can play range of blocks */
        #define	CDDOPAUSE	0x00000100
        	/* Output can be paused */
        #define	CDDORESUME	0x00000200
        	/* Output can be resumed */
        #define	CDDORESET	0x00000400
        	/* Drive can be completely reset */
        #define	CDDOSTART	0x00000800
        	/* Audio can be started */
        #define CDDOSTOP	0x00001000
        	/* Audio can be stopped */
        #define CDDOPITCH	0x00002000
        	/* Audio pitch can be changed */
        	u_long	routing_function;
        #define CDREADVOLUME	0x00000001
        	/* Volume settings can be read */
        #define CDSETVOLUME	0x00000002
        	/* Volume settings can be set */
        #define	CDSETMONO	0x00000100
        	/* Output can be set to mono */
        #define CDSETSTEREO	0x00000200
        	/* Output can be set to stereo (def) */
        #define	CDSETLEFT	0x00000400
        	/* Output can be set to left only */
        #define	CDSETRIGHT	0x00000800
        	/* Output can be set to right only */
        #define	CDSETMUTE	0x00001000
        	/* Output can be muted */
        #define CDSETPATCH	0x00008000
        	/* Direct routing control allowed */
        	u_long	special_function;
        #define	CDDOEJECT	0x00000001
        	/* The tray can be opened */
        #define	CDDOCLOSE	0x00000002
        	/* The tray can be closed */
        #define	CDDOLOCK	0x00000004
        	/* The tray can be locked */
        #define CDREADHEADER	0x00000100
        	/* Can read Table of Contents */
        #define	CDREADENTRIES	0x00000200
        	/* Can read TOC Entries */
        #define	CDREADSUBQ	0x00000200
        	/* Can read Subchannel info */
        #define CDREADRW	0x00000400
        	/* Can read subcodes R-W */
        #define	CDHASDEBUG	0x00004000
        	/* The tray has dynamic debugging */
        };

CDIOCPLAYTRACKS
    (struct ioc_play_track) Start audio playback given a track address and length. The structure is defined as follows:

        struct ioc_play_track
        {
        	u_char	start_track;
        	u_char	start_index;
        	u_char	end_track;
        	u_char	end_index;
        };

CDIOCPLAYBLOCKS
    (struct ioc_play_blocks) Start audio playback given a block address and length. The structure is defined as follows:

        struct ioc_play_blocks
        {
        	int	blk;
        	int	len;
        };

CDIOCPLAYMSF
    (struct ioc_play_msf) Start audio playback given a `minutes-seconds-frames' address and length. The structure is defined as follows:

        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;
        };

CDIOCREADSUBCHANNEL
    (struct ioc_read_subchannel) Read information from the subchannel at the location specified by this structure:

        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;
        };

CDIOREADTOCHEADER
    (struct ioc_toc_header) Return summary information about the table of contents for the mounted CD-ROM. The information is returned into the following structure:

        struct ioc_toc_header {
        	u_short len;
        	u_char  starting_track;
        	u_char  ending_track;
        };

CDIOREADTOCENTRYS
    (struct ioc_read_toc_entry) Return information from the table of contents entries mentioned. (Yes, this command name is misspelled.) The argument structure is defined as follows:

        struct ioc_read_toc_entry {
        	u_char	address_format;
        	u_char	starting_track;
        	u_short	data_len;
        	struct  cd_toc_entry *data;
        };

    The requested data is written into an area of size data_len and pointed to by data.
CDIOCSETPATCH
    (struct ioc_patch) Attach various audio channels to various output channels. The argument structure is defined thusly:

        struct ioc_patch {
        	u_char	patch[4];
        	/* one for each channel */
        };

CDIOCGETVOL
CDIOCSETVOL
    (struct ioc_vol) Get (set) information about the volume settings of the output channels. The argument structure is as follows:

        struct	ioc_vol
        {
        	u_char	vol[4];
        	/* one for each channel */
        };

CDIOCSETMONO
    Patch all output channels to all source channels.
CDIOCSETSTEREO
    Patch left source channel to the left output channel and the right source channel to the right output channel.
CDIOCSETMUTE
    Mute output without changing the volume settings.
CDIOCSETLEFT
CDIOCSETRIGHT
    Attach both output channels to the left (right) source channel.
CDIOCSETDEBUG
CDIOCCLRDEBUG
    Turn on (off) debugging for the appropriate device.
CDIOCPAUSE
CDIOCRESUME
    Pause (resume) audio play, without resetting the location of the read-head.
CDIOCRESET
    Reset the drive.
CDIOCSTART
CDIOCSTOP
    Tell the drive to spin-up (-down) the CD-ROM.
CDIOCALLOW
CDIOCPREVENT
    Tell the drive to allow (prevent) manual ejection of the CD-ROM disc. Not all drives support this feature.
CDIOCEJECT
    Eject the CD-ROM.
CDIOCCLOSE
    Tell the drive to close its door and load the media. Not all drives support this feature.
CDIOCPITCH
    (struct ioc_pitch) For drives that support it, this command instructs the drive to play the audio at a faster or slower rate than normal. Values of speed between -32767 and -1 result in slower playback; a zero value indicates normal speed; and values from 1 to 32767 give faster playback. Drives with less than 16 bits of resolution will silently ignore less-significant bits. The structure is defined thusly:

        struct	ioc_pitch
        {
        	short	speed;
        };

In addition the general scsi(4) ioctls may be used with the cd driver, if used against the `whole disk' partition (i.e. /dev/rcd0c).

NOTES
When a CD-ROM is changed in a drive controlled by the cd 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.

The audio code in the cd driver only support SCSI-2 standard audio commands. Because many CD-ROM manufacturers have not followed the standard, there are many CD-ROM drives for which audio will not work. Some work is planned to support some of the more common `broken' CD-ROM drives; however, this is not yet under way.

FILES
/dev/cd[0-9][a-h]
    block mode CD-ROM devices
/dev/rcd[0-9][a-h]
    raw mode CD-ROM devices

DIAGNOSTICS
None.

SEE ALSO
scsi(4), sd(4), disklabel(5), disklabel(8)

BUGS
The names of the structures used for the third argument to ioctl() were poorly chosen, and a number of spelling errors have survived in the names of the ioctl() commands.

HISTORY
This cd driver appeared in 386BSD 0.1.