CD(4) BSD Kernel Interfaces Manual CD(4)NAMEcd — SCSI and ATAPI CD-ROM driver
SYNOPSIS
cd* at scsibus? target ? lun ?
cd1 at scsibus0 target 4 lun 0
cd* at atapibus? drive ? flags 0x0000
DESCRIPTION
The cd driver provides support for a Small Computer Systems Interface
(SCSI) bus and Advanced Technology Attachment Packet Interface (ATAPI)
Compact Disc-Read Only Memory (CD-ROM) 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 par‐
tition 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.
For the use of flags with ATAPI devices, see wd(4).
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 ini‐
tialized 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 argu‐
ment 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 fea‐
ture.
CDIOCEJECT Eject the CD-ROM.
CDIOCLOADUNLOAD Cause the ATAPI changer to load or unload discs.
CDIOCCLOSE Tell the drive to close its door and load the media.
Not all drives support this feature.
In addition the general scsi(4) ioctls may be used with the cd driver, if
used against the `whole disk' partition (i.e. /dev/rcd0d for the bebox
and i386 port, /dev/rcd0c for all other ports).
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 referenc‐
ing 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 com‐
mands. 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; how‐
ever, 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 ALSOintro(4), scsi(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.
BSD January 16, 1996 BSD
