XPT(4)

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>