.\" .\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD .\" .\" Copyright (c) 2020 Andriy Gapon .\" .\" 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..chip_type .It Va hint.pca954x..at The upstream .Xr iicbus 4 the .Nm instance is attached to. .It Va hint.pca954x..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 .