1.\" 2.\" SPDX-License-Identifier: BSD-2-Clause 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.Dd November 13, 2021 28.Dt PCA954X 4 29.Os 30.Sh NAME 31.Nm pca954x 32.Nd driver for PCA9548A I2C switch 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following line in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device pca954x" 39.Cd "device iicmux" 40.Cd "device iicbus" 41.Ed 42.Pp 43Alternatively, to load the driver as a 44module at boot time, place the following line in 45.Xr loader.conf 5 : 46.Bd -literal -offset indent 47pca954x_load="YES" 48.Ed 49.Sh DESCRIPTION 50The 51.Nm 52driver supports the PCA9548A I2C bus switch and compatible chips such as 53TCA9548A. 54It automatically connects an upstream I2C bus to one of several downstream 55buses as needed when slave devices on the downstream buses initiate I/O. 56More information on the automatic switching behavior is available in 57.Xr iicmux 4 . 58.Sh FDT CONFIGURATION 59On an 60.Xr FDT 4 61based system, an 62.Nm 63device node is defined as a child node of its upstream I2C bus. 64The children of the 65.Nm 66node are additional I2C buses, which will have their own I2C slave 67devices described in their child nodes. 68.Pp 69The 70.Nm 71driver attaches to nodes where the 72.Va compatible 73property is set to one of 74.Bl -bullet 75.It 76.Qq nxp,pca9548 77.El 78.Pp 79The 80.Nm 81driver supports the following optional properties in addition to the standard 82I2C mux properties: 83.Bl -tag -width i2c-mux-idle-disconnect 84.It Va i2c-mux-idle-disconnect 85if defined, forces the switch to disconnect all children in idle state. 86.El 87.Sh HINTS CONFIGURATION 88On a 89.Xr device.hints 5 90based system, these values are configurable for 91.Nm : 92.Bl -tag -width hint.pca954x.<unit>.chip_type 93.It Va hint.pca954x.<unit>.at 94The upstream 95.Xr iicbus 4 96the 97.Nm 98instance is attached to. 99.It Va hint.pca954x.<unit>.chip_type 100The type of the chip. 101At present, only 102.Qq pca9548 103is supported. 104.El 105.Pp 106When configured via hints, the driver automatically adds an 107.Xr iicbus 4 108instance for every downstream bus supported by the chip. 109There is currently no way to indicate used versus unused channels. 110.Sh SEE ALSO 111.Xr iicbus 4 , 112.Xr iicmux 4 113.Sh HISTORY 114The 115.Nm 116driver and this manual page was written by 117.An Andriy Gapon Aq Mt avg@FreeBSD.org . 118