pin, ball, or pad) to connect a signal from one of the SoC internal

For example, based on the actual device design, a single SoC chip

pin can perform any of these roles: SPI clock, I2C

Function selection is performed by the pinmux controller, a SoC

based systems, the pinmux controller is represented by a node in

the device tree.

Depending on the state the device is in (active, idle) it might

Each configuration is described by setting the pinctrl-N

nodes of the pinmux controller node.

pinctrl-0 is a default configuration that is applied in the

In addition to referring to pin configurations by index, they

can be referred to by name if the pinctrl-names property is set.

The value of pinctrl-names is a list of strings with names for each pinctrl-N

Client devices can request a specific configuration using
.Xr fdt_pinctrl_configure 9 
​and
​.Xr fdt_pinctrl_configure_by_name 9 .

The pinctrl driver should implement FDT_PINCTRL_CONFIGURE

calling fdt_pinctrl_register function, and call

to configure pins for all enabled devices (devices where

the "status" property is not set to "disabled").

provides an API for manipulating I/O pin configurations on

On the controller side, the standard newbus probe and
attach methods are implemented.
This driver also implements the

method, in which it calls the

function to register itself as a pinmux controller.

Then

is used to walk the device tree and configure pins specified by the pinctrl-0

If a client device requires a pin configuration change at some

point of its lifecycle, it uses the

The function fdt_pinctrl_configure is used

fdt_pinctrl_configure is used

The fdt_pinctrl_configure function is used

to request a pin configuration

described by the pinctrl-N property with index

to request the pin configuration with name

identifies each descendant of the pinctrl

node.
The pinctrl node is a pin configuration

.Fn fdt_pinctrl_configure_tree
walks through enabled devices in the device tree.
If the pinctrl-0 property contains references
to child nodes of the specified pinctrl device,
their pins are configured.