pca954x4
Driver for pca9548a i2c switch
Usage
To compile this driver into the kernel, place the following line in your kernel configuration file:
device pca954x device iicmux device iicbus
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
pca954x_load="YES"
Overview
The pca954x 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 iicmux(4).
FDT configuration
On an FDT(4) based system, an pca954x device node is defined as a child node of its upstream I2C bus. The children of the pca954x node are additional I2C buses, which will have their own I2C slave devices described in their child nodes.
The pca954x driver attaches to nodes where the compatible property is set to one of
-
"nxp,pca9548"
The pca954x driver supports the following optional properties in addition to the standard I2C mux properties:
- i2c-mux-idle-disconnect
-
if defined, forces the switch to disconnect all children in idle state.
Hints configuration
On a device.hints(5) based system, these values are configurable for pca954x:
- hint.pca954x.<unit>.at
-
The upstream iicbus(4) the
pca954xinstance is attached to. - hint.pca954x.<unit>.chip_type
-
The type of the chip. At present, only "pca9548" is supported.
When configured via hints, the driver automatically adds an iicbus(4) instance for every downstream bus supported by the chip. There is currently no way to indicate used versus unused channels.
Releases
14 releases since FreeBSD 13.1-RELEASE; the text changed 1 time.