The pin control subsystem
The pin control (pinctrl) subsystem allows managing pin muxing. In the DT, devices that need pins to be multiplexed in a certain way must declare the pin control configuration they need.
The pinctrl subsystem provides:
- Pin multiplexing, which allows for reusing the same pin for different purposes, such as one pin being a UART TX pin, GPIO line, or HSI data line. Multiplexing can affect groups of pins or individual pins.
- Pin configuration, applying electronic properties of pins such as pull-up, pull-down, driver strength, debounce period, and so on.
The purpose of this book is limited to using functions exported by the pin controller driver, and does not cover how to write a pin controller driver.
Pinctrl and the device tree
The pinctrl subsystem is nothing but a way to gather pins (not only GPIO), and pass them to the driver. The pin controller driver is responsible for parsing pin descriptions in the DT and applying their configuration in the chip. The driver usually...
