CD(4) | Device Drivers Manual | CD(4) |
cd
— ATAPI and
SCSI CD-ROM driver
cd* at scsibus?
#cd0 at scsibus0 target 6 lun 0
(fixed-configuration
example)
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.
The following
ioctl(2) calls which apply to
CD-ROM drives are defined in the header files
<sys/cdio.h>
and
<sys/dkio.h>
.
DIOCGDINFO
,
DIOCSDINFO
struct disklabel
*CDIOCPLAYTRACKS
struct ioc_play_track *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 *struct ioc_play_blocks { int blk; int len; };
CDIOCPLAYMSF
struct ioc_play_msf *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 *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 *struct ioc_toc_header { u_short len; u_char starting_track; u_char ending_track; };
CDIOREADTOCENTRIES
struct ioc_read_toc_entry *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 *struct ioc_patch { u_char patch[4]; /* one for each channel */ };
CDIOCGETVOL
,
CDIOCSETVOL
struct ioc_vol
*struct ioc_vol { u_char vol[4]; /* one for each channel */ };
CDIOCSETMONO
CDIOCSETSTEREO
CDIOCSETMUTE
CDIOCSETLEFT
,
CDIOCSETRIGHT
CDIOCSETDEBUG
,
CDIOCCLRDEBUG
CDIOCPAUSE
,
CDIOCRESUME
CDIOCRESET
CDIOCSTART
,
CDIOCSTOP
CDIOCALLOW
,
CDIOCPREVENT
CDIOCEJECT
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).
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.
None.
cdio(1), eject(1), ioctl(2), intro(4), scsi(4), scsibus(4), sd(4), wd(4), disklabel(5), disklabel(8)
The cd
driver appeared in 386BSD 0.1.
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.
August 27, 2015 | OpenBSD-6.8 |