115 lines
4.0 KiB
Groff
115 lines
4.0 KiB
Groff
.\"
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.\" Copyright (c) 1998, 1999 Kenneth D. Merry.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 10, 1998
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.Dt PASS 4
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.Os FreeBSD 3.0
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.Sh NAME
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.Nm pass
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.Nd CAM application passthrough driver
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.Sh SYNOPSIS
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.Cd device pass0
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.Cd device pass2 at scbus0 target 3 unit 0
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.Sh DESCRIPTION
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The
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.Nm pass
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driver provides a way for userland applications to issue CAM CCBs to the
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kernel.
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.Pp
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Since the
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.Nm pass
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driver allows direct access to the CAM subsystem, system administrators
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should exercise caution when granting access to this driver. If used
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improperly, this driver can allow userland applications to crash a machine
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or cause data loss.
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.Pp
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The
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.Nm pass
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driver attaches to every
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.Tn SCSI
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device found in the system.
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Since it attaches to every device, it provides a generic means of accessing
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.Tn SCSI
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devices, and allows the user to access devices which have no
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"standard" peripheral driver associated with them.
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.Sh KERNEL CONFIGURATION
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It is only necessary to configure one
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.Nm pass
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device in the kernel;
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.Nm pass
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devices are automatically allocated as
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.Tn SCSI
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devices are found.
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.Sh IOCTLS
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.Bl -tag -width 012345678901234
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.It CAMIOCOMMAND
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This ioctl takes most kinds of CAM CCBs and passes them through to the CAM
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transport layer for action. Note that some CCB types are not allowed
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through the passthrough device, and must be sent through the
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.Xr xpt 4
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device instead. Some examples of xpt-only CCBs are XPT_SCAN_BUS,
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XPT_DEV_MATCH, XPT_RESET_BUS, XPT_SCAN_LUN, XPT_ENG_INQ, and XPT_ENG_EXEC.
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These CCB types have various attributes that make it illogical or
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impossible to service them through the passthrough interface.
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.It CAMGETPASSTHRU
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This ioctl takes an XPT_GDEVLIST CCB, and returns the passthrough device
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corresponding to the device in question. Although this ioctl is available
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through the
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.Nm pass
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driver, it is of limited use, since the caller must already know that
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the device in question is a passthrough device if they're issuing this
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ioctl. It is probably more useful to issue this ioctl through the
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.Xr xpt 4
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device.
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.El
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.Sh FILES
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.Bl -tag -width 01234567890 -compact
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.It Pa /dev/pass Ns Ar n
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Character device nodes for the
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.Nm pass
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driver. There should be one of these for each device accessed through the
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CAM subsystem.
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.El
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.Sh DIAGNOSTICS
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None.
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.Sh SEE ALSO
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.Xr cam 3 ,
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.Xr cam_cdbparse 3 ,
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.Xr xpt 4 ,
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.Xr camcontrol 8
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.Sh HISTORY
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The CAM passthrough driver first appeared in
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.Fx 3.0 .
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.Sh AUTHORS
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.An Kenneth Merry Aq ken@FreeBSD.ORG
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.Sh BUGS
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It might be nice to have a way to asynchronously send CCBs through the
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passthrough driver. This would probably require some sort of read/write
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interface or an asynchronous ioctl interface.
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