4d846d260e
The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch up to that fact and revert to their recommended match of BSD-2-Clause. Discussed with: pfg MFC After: 3 days Sponsored by: Netflix
120 lines
3.5 KiB
Groff
120 lines
3.5 KiB
Groff
.\"
|
|
.\" SPDX-License-Identifier: BSD-2-Clause
|
|
.\"
|
|
.\" Copyright (c) 2020 Andriy Gapon <avg@FreeBSD.org>
|
|
.\"
|
|
.\" 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 November 13, 2021
|
|
.Dt PCA954X 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm pca954x
|
|
.Nd driver for PCA9548A I2C switch
|
|
.Sh SYNOPSIS
|
|
To compile this driver into the kernel,
|
|
place the following line in your
|
|
kernel configuration file:
|
|
.Bd -ragged -offset indent
|
|
.Cd "device pca954x"
|
|
.Cd "device iicmux"
|
|
.Cd "device iicbus"
|
|
.Ed
|
|
.Pp
|
|
Alternatively, to load the driver as a
|
|
module at boot time, place the following line in
|
|
.Xr loader.conf 5 :
|
|
.Bd -literal -offset indent
|
|
pca954x_load="YES"
|
|
.Ed
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
driver supports the PCA9548A I2C bus switch and compatible chips such as
|
|
TCA9548A.
|
|
It automatically connects an upstream I2C bus to one of several downstream
|
|
buses as needed when slave devices on the downstream buses initiate I/O.
|
|
More information on the automatic switching behavior is available in
|
|
.Xr iicmux 4 .
|
|
.Sh FDT CONFIGURATION
|
|
On an
|
|
.Xr FDT 4
|
|
based system, an
|
|
.Nm
|
|
device node is defined as a child node of its upstream I2C bus.
|
|
The children of the
|
|
.Nm
|
|
node are additional I2C buses, which will have their own I2C slave
|
|
devices described in their child nodes.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver attaches to nodes where the
|
|
.Va compatible
|
|
property is set to one of
|
|
.Bl -bullet
|
|
.It
|
|
.Qq nxp,pca9548
|
|
.El
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver supports the following optional properties in addition to the standard
|
|
I2C mux properties:
|
|
.Bl -tag -width i2c-mux-idle-disconnect
|
|
.It Va i2c-mux-idle-disconnect
|
|
if defined, forces the switch to disconnect all children in idle state.
|
|
.El
|
|
.Sh HINTS CONFIGURATION
|
|
On a
|
|
.Xr device.hints 5
|
|
based system, these values are configurable for
|
|
.Nm :
|
|
.Bl -tag -width hint.pca954x.<unit>.chip_type
|
|
.It Va hint.pca954x.<unit>.at
|
|
The upstream
|
|
.Xr iicbus 4
|
|
the
|
|
.Nm
|
|
instance is attached to.
|
|
.It Va hint.pca954x.<unit>.chip_type
|
|
The type of the chip.
|
|
At present, only
|
|
.Qq pca9548
|
|
is supported.
|
|
.El
|
|
.Pp
|
|
When configured via hints, the driver automatically adds an
|
|
.Xr iicbus 4
|
|
instance for every downstream bus supported by the chip.
|
|
There is currently no way to indicate used versus unused channels.
|
|
.Sh SEE ALSO
|
|
.Xr iicbus 4 ,
|
|
.Xr iicmux 4
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver and this manual page was written by
|
|
.An Andriy Gapon Aq Mt avg@FreeBSD.org .
|