cd

CD(9)                     BSD Kernel Developer's Manual                    CD(9)

NAME
     cd — CDROM driver for the CAM SCSI subsystem

DESCRIPTION
     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 commands.
     Some drives do not behave as the driver expects.  See the QUIRKS section
     for information on possible flags.

QUIRKS
     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 unimplemented 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 flag.

     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 changer.

     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.

     CD_Q_10_BYTE_ONLY
                      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 several
                      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
                      commands.  (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.

FILES
     /sys/cam/scsi/scsi_cd.c  is the driver source file.

SEE ALSO
     cd(4), scsi(4)

HISTORY
     The cd manual page first appeared in FreeBSD 2.2.

AUTHORS
     This manual page was written by John-Mark Gurney <gurney_j@efn.org>.  It
     was updated for CAM and FreeBSD 3.0 by Kenneth Merry <ken@FreeBSD.org>.

BSD                             September 2, 2003                            BSD