freebsd-skq/share/man/man4/pass.4

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.\"	$Id: pass.4,v 1.1 1998/10/12 00:26:03 ken Exp $
.\"
.Dd October 10, 1998
.Dt PASS 4
.Os FreeBSD 3.0
.Sh NAME
.Nm pass
.Nd CAM application passthrough driver
.Sh SYNOPSIS
.Cd device pass0
.Cd device pass2 at scbus0 target 3 lun 0
.Sh DESCRIPTION
The
.Nm pass
driver provides a way for userland applications to issue CAM CCBs to the
kernel. 
.Pp
Since the
.Nm pass
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.
.Pp
The
.Nm pass
driver attaches to every
.Tn SCSI
device found in the system.
Since it attaches to every device, it provides a generic means of accessing
.Tn SCSI
devices, and allows the user to access devices which have no
"standard" peripheral driver associated with them.
.Sh KERNEL CONFIGURATION
It is only necessary to configure one
.Nm pass
device in the kernel;
.Nm pass
devices are automatically allocated as
.Tn SCSI
devices are found.
.Sh IOCTLS
.Bl -tag -width 012345678901234
.It CAMIOCOMMAND
This ioctl takes any kind of CAM CCB and passes it through to the CAM
transport layer for action.
.It CAMGETPASSTHRU
This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device
corresponding to the device in question.  Although this ioctl is available
through the
.Nm pass
driver, it is of limited use, since the caller must already know that
the device in question is a passthrough device if they're issuing this
ioctl.  It is probably more useful to issue this ioctl through the
.Xr xpt 4
device.
.El
.Sh FILES
.Bl -tag -width 01234567890 -compact
.It Pa /dev/pass Ns Ar n
Character device nodes for the
.Nm pass
driver.  There should be one of these for each device accessed through the
CAM subsystem.
.El
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO
.Xr cam 3 ,
.Xr cam_cdbparse 3 ,
.Xr xpt 4 ,
.Xr camcontrol 8
.Sh HISTORY
The CAM passthrough driver first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An Kenneth Merry Aq ken@FreeBSD.ORG
.Sh BUGS
It might be nice to have a way to asynchronously send CCBs through the
passthrough driver.  This would probably require some sort of read/write
interface or an asynchronous ioctl interface.