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.\" Copyright (c) 1998 Kenneth D. Merry.
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.Dd October 10, 1998
.Dt XPT 4
.Os
.Sh NAME
.Nm xpt
.Nd CAM transport layer interface
.Sh SYNOPSIS
None.
.Sh DESCRIPTION
The
.Nm
driver provides a way for userland applications to issue certain CAM CCBs
to the kernel.
.Pp
Since the
.Nm
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.
.Sh KERNEL CONFIGURATION
There is no kernel configuration required for the
.Nm
driver.
It is enabled when
.Tn 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.
.Sh IOCTLS
.Bl -tag -width 01234567890123
.It 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:
.Pp
.Bl -tag -width XPT_DEV_MATCH -compact
.It XPT_SCAN_BUS
.It XPT_RESET_BUS
.It XPT_SCAN_LUN
.It XPT_ENG_INQ
.It XPT_ENG_EXEC
.It XPT_DEBUG
.It XPT_DEV_MATCH
.It XPT_PATH_INQ
.El
.Pp
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
.Tn SCSI
device.
.It CAMGETPASSTHRU
This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device
corresponding to the device in question.
.El
.Sh FILES
.Bl -tag -width /dev/xpt0 -compact
.It Pa /dev/xpt0
Character device node for the
.Nm
driver.
.El
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO
.Xr cam 3 ,
.Xr cam_cdbparse 3 ,
.Xr pass 4 ,
.Xr camcontrol 8
.Sh HISTORY
The CAM transport layer driver first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An Kenneth Merry Aq Mt ken@FreeBSD.org