cd —
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 commands. 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 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.
- /sys/cam/scsi/scsi_cd.c
- is the driver source file.
cd(4),
scsi(4)
The
cd manual page first appeared in
FreeBSD 2.2.
This manual page was written by
John-Mark
Gurney
<
[email protected]>.
It was updated for CAM and
FreeBSD 3.0 by
Kenneth Merry
<
[email protected]>.