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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>.