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cd(9freebsd)


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.



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