CD(4) OpenBSD Programmer's Manual CD(4)NAMEcd - ATAPI and SCSI CD-ROM driver
SYNOPSIS
cd* at scsibus?
#cd0 at scsibus0 target 6 lun 0 (fixed-configuration example)
DESCRIPTION
The cd driver provides support for ATAPI and SCSI CD-ROM (Compact Disc
Read-Only Memory) drives, via scsibus(4). 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'' and
``removable'' CD-ROM or WORM devices will be ``attached'' to the cd
driver.
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.
IOCTLS
The following ioctl(2) calls which apply to 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).
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.
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 supports 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-p] block mode CD-ROM devices
/dev/rcd[0-9][a-p] raw mode CD-ROM devices
DIAGNOSTICS
None.
SEE ALSOcdio(1), eject(1), ioctl(2), intro(4), scsi(4), scsibus(4), sd(4), wd(4),
disklabel(5), disklabel(8)HISTORY
The cd driver appeared in 386BSD 0.1.
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.
OpenBSD 4.9 June 1, 2007 OpenBSD 4.9
