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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