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.\"
.\" Copyright (c) 2016-2019 Alexander Motin <mav@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 29, 2019
.Dt NTB_TRANSPORT 4
.Os
.Sh NAME
.Nm ntb_transport
.Nd Packet-oriented transport for Non-Transparent Bridges
.Sh SYNOPSIS
To compile this driver into your kernel,
place the following lines in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device ntb"
.Cd "device ntb_transport"
.Ed
.Pp
Or, to load the driver as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
ntb_transport_load="YES"
.Ed
.Pp
The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hw.ntb_transport.debug_level
Driver debug level.
The default value is 0, higher means more verbose.
.It Va hw.ntb_transport.max_mw_size
Limits maximum memory window usage.
Allocation of big physically contiguous memory buffer may be a problem,
while too big buffers makes no much sense for low latency network interface.
.It Va hint.ntb_transport. Ns Ar X Ns Va .config
Configures a set of the transport consumers, separated by commas.
Each consumer can be configured as: "[<name>][:<queues>]", where:
.Va name
is a name of the driver to attach (empty means any),
.Va queues
is a number of queues to allocate (empty means automatic).
The default configuration is empty string, which means single consumer
with one queue per memory window, allowing any driver to attach.
.El
.Sh DESCRIPTION
The
.Nm
driver attaches on top of the
.Nm ntb
driver to utilize its resources to create a set of bidirectional queues,
delivering packets between the systems.
The primary purpose of this driver is to be used by
.Nm if_ntb
network interface, but other consumers may also be developed using KPI.
.Pp
Each
.Nm
require from underlying
.Nm ntb
instance:
.Bl -bullet -compact
.It
1 or more memory windows;
.It
6 scratchpads, plus 2 more for each additional memory window;
.It
1 doorbell for each memory window or configured queue.
.El
.Sh SEE ALSO
.Xr if_ntb 4 ,
.Xr ntb 4 ,
.Xr ntb_hw_amd 4 ,
.Xr ntb_hw_intel 4 ,
.Xr ntb_hw_plx 4
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was developed by Intel and originally written by
.An Carl Delsey Aq Mt carl@FreeBSD.org .
Later improvements were done by
.An Conrad E. Meyer Aq Mt cem@FreeBSD.org
and
.An Alexander Motin Aq Mt mav@FreeBSD.org .
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