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>