CD(9) BSD Kernel Developer's Manual CD(9)NAMEcd — CDROM driver for the CAM SCSI subsystem
The cd device driver provides a read only interface for CDROM drives
(SCSI type 5) and WORM drives (SCSI type 4) that support CDROM type com‐
mands. Some drives do not behave as the driver expects. See the QUIRKS
section for information on possible flags.
Each CD-ROM device can have different interpretations of the SCSI spec.
This can lead to drives requiring special handling in the driver. The
following is a list of quirks that the driver recognize.
CD_Q_NO_TOUCH This flag tell the driver not to probe the drive at
attach time to see if there is a disk in the drive and
find out what size it is. This flag is currently unim‐
plemented in the CAM cd driver.
CD_Q_BCD_TRACKS This flag is for broken drives that return the track
numbers in packed BCD instead of straight decimal. If
the drive seems to skip tracks (tracks 10-15 are
skipped) then you have a drive that is in need of this
CD_Q_NO_CHANGER This flag tells the driver that the device in question
is not a changer. This is only necessary for a CDROM
device with multiple luns that are not a part of a
CD_Q_CHANGER This flag tells the driver that the given device is a
multi-lun changer. In general, the driver will figure
this out automatically when it sees a LUN greater than
0. Setting this flag only has the effect of telling the
driver to run the initial read capacity command for LUN
0 of the changer through the changer scheduling code.
This flag tells the driver that the given device only
accepts 10 byte MODE SENSE/MODE SELECT commands. In
general these types of quirks should not be added to the
cd(4) driver. The reason is that the driver does sev‐
eral things to attempt to determine whether the drive in
question needs 10 byte commands. First, it issues a CAM
Path Inquiry command to determine whether the protocol
that the drive speaks typically only allows 10 byte com‐
mands. (ATAPI and USB are two prominent examples of
protocols where you generally only want to send 10 byte
commands.) Then, if it gets an ILLEGAL REQUEST error
back from a 6 byte MODE SENSE or MODE SELECT command, it
attempts to send the 10 byte version of the command
instead. The only reason you would need a quirk is if
your drive uses a protocol (e.g., SCSI) that typically
does not have a problem with 6 byte commands.
/sys/cam/scsi/scsi_cd.c is the driver source file.
SEE ALSOcd(4), scsi(4)HISTORY
The cd manual page first appeared in FreeBSD 2.2.
This manual page was written by John-Mark Gurney ⟨email@example.com⟩. It
was updated for CAM and FreeBSD 3.0 by Kenneth Merry ⟨ken@FreeBSD.org⟩.
BSD September 2, 2003 BSD