134 lines
4.5 KiB
Groff
134 lines
4.5 KiB
Groff
.\" $NetBSD: ubt.4,v 1.6 2006/09/10 20:09:11 plunky Exp $
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.\"
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.\" Copyright (c) 2006 Itronix Inc.
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.\" All rights reserved.
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.\"
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.\" Written by Iain Hibbert for Itronix Inc.
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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 Itronix Inc. may not be used to endorse
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.\" or promote products derived from this software without specific
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.\" prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY ITRONIX INC. ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd August 27, 2006
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.Dt UBT 4
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.Os
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.Sh NAME
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.Nm ubt
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.Nd USB Bluetooth driver
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.Sh SYNOPSIS
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.Cd "ubt* at uhub? port ? configuration ? interface ?"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for USB Bluetooth dongles
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to the Bluetooth protocol stack.
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.Pp
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USB Bluetooth dongles provide two interfaces, both of which the
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.Nm
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driver claims.
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The second interface is used for Isochronous data and will have
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several alternate configurations regarding bandwidth consumption,
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which can be set using the hw.ubtN.config
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.Xr sysctl 8
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variable.
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The number of alternate configurations is indicated by the value
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in the hw.ubtN.alt_config variable, and the isoc frame size for the current
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configuration is shown in the hw.ubtN.sco_rxsize and hw.ubtN.sco_txsize
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variables.
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.Pp
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By default, configuration 0 is selected, which means that no bandwidth
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is used on the Isochronous interface and no SCO data can be sent.
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Consult the Bluetooth USB specification at https://www.bluetooth.org/
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for complete instructions on setting bandwidth consumption.
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The following extract may be
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useful as a general guidance though details may differ between manufacturers.
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.Pp
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.Bl -tag -compact -width XXX
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.It 0
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No active voice channels
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.It 1
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One voice channel with 8-bit encoding
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.It 2
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Two voice channels with 8-bit encoding, or one voice channel with
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16-bit encoding.
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.It 3
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Three voice channels with 8-bit encoding
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.It 4
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Two voice channels with 16-bit encoding
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.It 5
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Three voice channels with 16-bit encoding
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.El
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.Sh SEE ALSO
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.Xr bluetooth 4 ,
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.Xr uhub 4 ,
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.Xr sysctl 8
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.Sh HISTORY
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This
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.Nm
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device driver was originally a character device written by
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.An David Sainty
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and
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.An Lennart Augustsson .
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It was rewritten to support socket based Bluetooth access for
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.Nx 4.0
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by
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.An Iain Hibbert .
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.Sh CAVEATS
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Isochronous data is seemingly not well supported over USB in the current
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system and to get SCO working, you may have to calculate the SCO packet
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size that the stack will use.
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This is the sco_mtu value reported by the
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.Xr btconfig 8
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command, and when combined with the SCO header (3 bytes) should
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fit exactly into an integer number of Isochronous data frames where
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the frame size is indicated by the
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.Sq hw.ubtN.sco_txsize
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sysctl variable.
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.Pp
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For example: I want one voice channel (which is all that is supported,
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for now) so am using configuration #2, with a frame length of 17
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bytes.
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This gives possible values of:
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.Pp
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.Dl "(17 * 1) - 3 = 14"
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.Dl "(17 * 2) - 3 = 31"
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.Dl "(17 * 3) - 3 = 48"
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.Dl "(17 * 4) - 3 = 65"
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.Dl "(17 * 5) - 3 = 82"
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.Dl "etc."
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.Pp
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.Xr btconfig 8
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shows the maximum SCO payload as 64 bytes, so I am using the next smaller
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size of 48, to minimize the overhead of the 3 header bytes.
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.Pp
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The SCO packet size can be changed using the
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.Sq scomtu
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option to
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.Xr btconfig 8 .
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.Pp
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The failure mode is that the USB Bluetooth dongle locks up though
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generally removal/reinsertion will clear the problem.
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.Sh BUGS
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The Isochronous configuration can only be changed when the device is not
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marked up.
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