---
name: "xpt"
section: "4"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/xpt"
---

# xpt(4)

CAM transport layer interface

## 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/3.md), [cam\_cdbparse(3)](/cam_cdbparse/3.md), [pass(4)](/pass/4.md), [camcontrol(8)](/camcontrol/8.md)

## HISTORY

The CAM transport layer driver first appeared in FreeBSD 3.0.

## AUTHORS

Kenneth Merry ⟨ken@FreeBSD.org⟩