Linux Device Drivers Development

GPIO descriptor mapping - the device tree

GPIO descriptor mappings are defined in the consumer device's node. The property that contains a GPIO descriptor mapping must be named <name>-gpios or <name>-gpio, where <name> is meaningful enough to describe the function for which those GPIOs will be used.

You should always suffix the property name with either -gpio or -gpios because every descriptor-based interface function relies on the gpio_suffixes[] variable, defined in drivers/gpio/gpiolib.h and shown as follows:

/* gpio suffixes used for ACPI and device tree lookup */ 
static const char * const gpio_suffixes[] = { "gpios", "gpio" }; 

Let's see how to do this by having a look at the function used to look for GPIO descriptor mappings in devices ...