NTB_TRANSPORT(4)       FreeBSD Kernel Interfaces Manual       NTB_TRANSPORT(4)

NAME
     ntb_transport - Packet-oriented transport for Non-Transparent Bridges

SYNOPSIS
     To compile this driver into your kernel, place the following lines in
     your kernel configuration file:

           device ntb
           device ntb_transport

     Or, to load the driver as a module at boot, place the following line in
     loader.conf(5):

           ntb_transport_load="YES"

     The following tunables are settable from the loader(8):

     hw.ntb_transport.debug_level
     Driver debug level.  The default value is 0, higher means more verbose.

     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.

     hint.ntb_transport.X.config
     Configures a set of the transport consumers, separated by commas.  Each
     consumer can be configured as: "[<name>][:<queues>]", where: name is a
     name of the driver to attach (empty means any), 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.

     hint.ntb_transport.X.compact
     Non-zero value enables compact version of scratchpad protocol, using half
     as many registers.  Enabled automatically if there is not enough
     registers to negotiate all available memory windows.  The compact version
     does not support memory windows of 4GB and above.

DESCRIPTION
     The ntb_transport driver attaches on top of the 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
     if_ntb network interface, but other consumers may also be developed using
     KPI.

     Each ntb_transport require from underlying ntb instance:
     •   1 or more memory windows;
     •   6 scratchpads, plus 2 more for each additional memory window, or 3
         plus 1 in case of compact protocol;
     •   1 doorbell for each memory window or configured queue.

SEE ALSO
     if_ntb(4), ntb(4), ntb_hw_amd(4), ntb_hw_intel(4), ntb_hw_plx(4)

AUTHORS
     The ntb_transport driver was developed by Intel and originally written by
     Carl Delsey <carl@FreeBSD.org>.  Later improvements were done by Conrad
     E. Meyer <cem@FreeBSD.org> and Alexander Motin <mav@FreeBSD.org>.

FreeBSD 13.1-RELEASE-p6        November 9, 2019        FreeBSD 13.1-RELEASE-p6