120 lines
3.5 KiB
Groff
120 lines
3.5 KiB
Groff
.\"
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.\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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.\"
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.\" Copyright (c) 2020 Andriy Gapon <avg@FreeBSD.org>
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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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.\"
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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 November 13, 2021
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.Dt PCA954X 4
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.Os
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.Sh NAME
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.Nm pca954x
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.Nd driver for PCA9548A I2C switch
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device pca954x"
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.Cd "device iicmux"
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.Cd "device iicbus"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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pca954x_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver supports the PCA9548A I2C bus switch and compatible chips such as
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TCA9548A.
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It automatically connects an upstream I2C bus to one of several downstream
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buses as needed when slave devices on the downstream buses initiate I/O.
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More information on the automatic switching behavior is available in
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.Xr iicmux 4 .
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.Sh FDT CONFIGURATION
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On an
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.Xr FDT 4
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based system, an
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.Nm
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device node is defined as a child node of its upstream I2C bus.
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The children of the
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.Nm
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node are additional I2C buses, which will have their own I2C slave
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devices described in their child nodes.
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.Pp
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The
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.Nm
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driver attaches to nodes where the
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.Va compatible
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property is set to one of
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.Bl -bullet
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.It
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.Qq nxp,pca9548
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.El
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.Pp
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The
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.Nm
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driver supports the following optional properties in addition to the standard
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I2C mux properties:
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.Bl -tag -width i2c-mux-idle-disconnect
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.It Va i2c-mux-idle-disconnect
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if defined, forces the switch to disconnect all children in idle state.
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.El
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.Sh HINTS CONFIGURATION
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On a
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.Xr device.hints 5
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based system, these values are configurable for
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.Nm :
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.Bl -tag -width hint.pca954x.<unit>.chip_type
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.It Va hint.pca954x.<unit>.at
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The upstream
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.Xr iicbus 4
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the
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.Nm
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instance is attached to.
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.It Va hint.pca954x.<unit>.chip_type
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The type of the chip.
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At present, only
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.Qq pca9548
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is supported.
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.El
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.Pp
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When configured via hints, the driver automatically adds an
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.Xr iicbus 4
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instance for every downstream bus supported by the chip.
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There is currently no way to indicate used versus unused channels.
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.Sh SEE ALSO
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.Xr iicbus 4 ,
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.Xr iicmux 4
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.Sh HISTORY
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The
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.Nm
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driver and this manual page was written by
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.An Andriy Gapon Aq Mt avg@FreeBSD.org .
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