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 tells 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  <jmg@FreeBSD.org>.   It  was  updated  for  CAM  and
       FreeBSD 3.0 by Kenneth Merry <ken@FreeBSD.org>.

Debian                                           March 25, 2014                                            CD(9)