NAME
cd —
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 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.
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
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.
-
-
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.
-
-
DIOCTUR
- Test unit ready - to allow userland to silently check for
presence of media.
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
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
intro(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.