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.\"
.\" Copyright (c) 2017 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:
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.\" $FreeBSD$
.\"
.Dd August 30, 2017
.Dt NTB 4
.Os
.Sh NAME
.Nm ntb
.Nd Non-Transparent Bridge subsystem
.Sh SYNOPSIS
To compile it into your kernel,
place the following lines in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device ntb"
.Ed
.Pp
Or, to load it as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
ntb_load="YES"
.Ed
.Pp
The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hw.ntb.debug_level
Driver debug level.
The default value is 0, higher means more verbose.
.It Va hint.ntb_hw. Ns Ar X Ns Va .config
Configures NTB resources split between several consumer devices.
Configuration of multiple consumer devices separated by commas.
Each device can be configured as: "[<name>][:<mw>[:<spad>[:<db>]]]", where:
.Va name
is a name of the driver which should attach the device (empty means any),
.Va mw
is a number of memory windows to allocate (empty means all available),
.Va spad
is a number of scratchpad registers to allocate (empty means all available),
.Va db
is a number of doorbells to allocate (empty means all available).
The default configuration is empty string, which means single device
with all available resources allowing any driver attachment.
.El
.Sh DESCRIPTION
Non-Transparent Bridges allow to connect two computer systems with PCIe
link(s), providing each of them limited access to others memory space,
scratchpad registers and interrupts.
The
.Nm
subsystem uses those resources provided in generic way by hardware drivers
and splits them between multiple consumer drivers, according to specified
configuration.
.Sh SEE ALSO
.Xr if_ntb 4 ,
.Xr ntb_transport 4 ,
.Xr ntb_hw_intel 4 ,
.Xr ntb_hw_plx 4
.Sh AUTHORS
.An -nosplit
The
.Nm
subsystem 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 .