1.\" 2.\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3.\" 4.\" Copyright (c) 2020 Andriy Gapon <avg@FreeBSD.org> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" $FreeBSD$ 28.\" 29.Dd November 13, 2021 30.Dt PCA954X 4 31.Os 32.Sh NAME 33.Nm pca954x 34.Nd driver for PCA9548A I2C switch 35.Sh SYNOPSIS 36To compile this driver into the kernel, 37place the following line in your 38kernel configuration file: 39.Bd -ragged -offset indent 40.Cd "device pca954x" 41.Cd "device iicmux" 42.Cd "device iicbus" 43.Ed 44.Pp 45Alternatively, to load the driver as a 46module at boot time, place the following line in 47.Xr loader.conf 5 : 48.Bd -literal -offset indent 49pca954x_load="YES" 50.Ed 51.Sh DESCRIPTION 52The 53.Nm 54driver supports the PCA9548A I2C bus switch and compatible chips such as 55TCA9548A. 56It automatically connects an upstream I2C bus to one of several downstream 57buses as needed when slave devices on the downstream buses initiate I/O. 58More information on the automatic switching behavior is available in 59.Xr iicmux 4 . 60.Sh FDT CONFIGURATION 61On an 62.Xr FDT 4 63based system, an 64.Nm 65device node is defined as a child node of its upstream I2C bus. 66The children of the 67.Nm 68node are additional I2C buses, which will have their own I2C slave 69devices described in their child nodes. 70.Pp 71The 72.Nm 73driver attaches to nodes where the 74.Va compatible 75property is set to one of 76.Bl -bullet 77.It 78.Qq nxp,pca9548 79.El 80.Pp 81The 82.Nm 83driver supports the following optional properties in addition to the standard 84I2C mux properties: 85.Bl -tag -width i2c-mux-idle-disconnect 86.It Va i2c-mux-idle-disconnect 87if defined, forces the switch to disconnect all children in idle state. 88.El 89.Sh HINTS CONFIGURATION 90On a 91.Xr device.hints 5 92based system, these values are configurable for 93.Nm : 94.Bl -tag -width hint.pca954x.<unit>.chip_type 95.It Va hint.pca954x.<unit>.at 96The upstream 97.Xr iicbus 4 98the 99.Nm 100instance is attached to. 101.It Va hint.pca954x.<unit>.chip_type 102The type of the chip. 103At present, only 104.Qq pca9548 105is supported. 106.El 107.Pp 108When configured via hints, the driver automatically adds an 109.Xr iicbus 4 110instance for every downstream bus supported by the chip. 111There is currently no way to indicate used versus unused channels. 112.Sh SEE ALSO 113.Xr iicbus 4 , 114.Xr iicmux 4 115.Sh HISTORY 116The 117.Nm 118driver and this manual page was written by 119.An Andriy Gapon Aq Mt avg@FreeBSD.org . 120