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XPT(4) Device Drivers Manual XPT(4)

xpt — CAM transport layer interface

None.

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.

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.

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.

This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device corresponding to the device in question.

/dev/xpt0
Character device node for the xpt driver.

None.

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

The CAM transport layer driver first appeared in FreeBSD 3.0.

Kenneth Merry <ken@FreeBSD.org>

October 10, 1998 DragonFly-5.6.1