NAME

       xpt — CAM transport layer interface

SYNOPSIS

       None.

DESCRIPTION

       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

       None.

SEE ALSO

       cam(3), cam_cdbparse(3), pass(4), camcontrol(8)

HISTORY

       The CAM transport layer driver first appeared in FreeBSD 3.0.

AUTHORS

       Kenneth Merry <ken@FreeBSD.org>

Debian                                          October 10, 1998                                          XPT(4)