gpiod_* vs gpio_* methods in the Linux Kernel

Question

Which of the GPIO APIs in Linux device driver programming is preferable and in what conditions: gpio_set_value() or gpiod_set_value()?

One takes the GPIO desc as the object while other takes the GPIO parsed from the device tree.

Answer 1

For all new drivers it's recommended to use gpiod_* API. Old gpio_* API is considered deprecated now.

From this commit:

gpiolib: export descriptor-based GPIO interface

This patch exports the gpiod_* family of API functions, a safer alternative to the legacy GPIO interface. Differences between the gpiod and legacy gpio APIs are:

• gpio works with integers, whereas gpiod operates on opaque handlers which cannot be forged or used before proper acquisition
• gpiod get/set functions are aware of the active low state of a GPIO
• gpio consumers should now include <linux/gpio/consumer.h> to access the new interface, whereas chips drivers will use <linux/gpio/driver.h>

The legacy gpio API is now built as inline functions on top of gpiod.

See next links for details on new gpiod API:

• [LWN article] GPIO in the kernel: future directions

• [Kernel documentation] GPIO Descriptor Consumer Interface

  (and rest of gpiod kernel documentation added by this commit)