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cd(9) [freebsd man page]

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

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 com- mands. 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 auto- matically 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 exam- ples 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 <>. It was updated for CAM and FreeBSD 3.0 by Kenneth Merry <>. BSD
March 25, 2014 BSD

Check Out this Related Man Page

XPT(4)                                                     BSD Kernel Interfaces Manual                                                     XPT(4)

xpt -- CAM transport layer interface SYNOPSIS
The xpt driver provides a way for userland applications to issue certain CAM CCBs to the kernel. Since the xpt driver allows direct access to the CAM subsystem, system administrators should exercise caution when granting access to this driver. If used improperly, this driver can allow userland applications to crash a machine or cause data loss. KERNEL CONFIGURATION
There is no kernel configuration required for the xpt driver. It is enabled when SCSI support is enabled in the kernel. There is one instance of the xpt driver per CAM transport layer instance. Since there is currently only one CAM transport layer, there will only be one instance of this driver. IOCTLS
CAMIOCOMMAND This ioctl takes certain kinds of CAM CCBs and passes them through to the CAM transport layer for action. Only the following CCB types are supported: XPT_SCAN_BUS XPT_RESET_BUS XPT_SCAN_LUN XPT_ENG_INQ XPT_ENG_EXEC XPT_DEBUG XPT_DEV_MATCH XPT_PATH_INQ The above CCBs are the only ones supported since it makes more sense to send them through a generic passthrough device rather than a passthrough device tied to a particular underlying SCSI device. CAMGETPASSTHRU This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device corresponding to the device in question. FILES
/dev/xpt0 Character device node for the xpt driver. DIAGNOSTICS
cam(3), cam_cdbparse(3), pass(4), camcontrol(8) HISTORY
The CAM transport layer driver first appeared in FreeBSD 3.0. AUTHORS
Kenneth Merry <> BSD October 10, 1998 BSD
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