gpio_demo.dtsi

#include "bone/black.h"
#include "gpio.h"

// Since we're creating a virtual device, there's not really a better place to
// put it than root of the device tree.
/ {
	// Node name "gpios" is arbitrary but should not conflict with other
	// nodes or properties in the root of the device tree.
	// To list all of these on a running system:  ls /proc/device-tree/
	gpios {
		// configure the driver for this device node, which must be "gpio-of-helper"
		compatible = "gpio-of-helper";

		// Attach pinmux node to this device node.  In rare cases devices may have
		// multiple pinmux states, but usually you only have a "default" state.
		pinctrl-names = "default";
		pinctrl-0 = <&gpio_pins>;  //<--- references the "gpio_pins:" label below

		// For each gpio to be setup {

		// The node name "gpio-label" becomes the gpio label and may be arbitrary but
		// must be unique for each gpio (globally, not merely those exported by this
		// gpio-of-helper device).
		gpio-label {
			gpio = <
				&gpio2		// gpio controller (&gpio0, &gpio1, &gpio2, or &gpio3)
				2		// gpio of that controller (0-31)
				ACTIVE_LOW	// either ACTIVE_HIGH (normal) or ACTIVE_LOW (inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-high;		// if output, whether it's initially low or initially high

			// Specifying either "init-low;" or "init-high;" is forbidden for inputs and
			// required for outputs, hence its presence automatically implies the gpio is
			// configured as output hence explicitly specifying "output;" is optional.
			//
			// init-low/high is not affected by whether the gpio is ACTIVE_HIGH or ACTIVE_LOW.

			// If you want userspace to be able to change the direction of the gpio from
			// input to output or vice versa, uncomment the following:
			//dir-changeable;
		};
		MS1-P8_10 {
			gpio = <
				&gpio2		
				4	
				ACTIVE_LOW	inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-low;		// if output, whether it's initially low or initially high
		};
		MS2-P8_11 {
			gpio = <
				&gpio1		
				13
				ACTIVE_LOW	inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-low;		// if output, whether it's initially low or initially high
		};
		enable-P8_12 {
			gpio = <
				&gpio1		
				12
				ACTIVE_LOW	inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-low;		// if output, whether it's initially low or initially high
		};
		direction-P8_13 {
			gpio = <
				&gpio0		
				23
				ACTIVE_LOW	inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-low;		// if output, whether it's initially low or initially high
		};
		step-P8_14 {
			gpio = <
				&gpio0		
				26
				ACTIVE_LOW	inverted)
			>;
			output;			// initial direction: input or output (optional for outputs)
			init-low;		// if output, whether it's initially low or initially high
		};
	};
};

// Pinmux nodes must be created inside the pinmux controller, which is &am33xx_pinmux
&am33xx_pinmux {
	// Label "gpio_pins" is arbitrary but must be _globally_ unique among all labels
	// in the device tree (base + overlays), hence it's a good idea to make a bit more
	// verbose than the node name needs to be.  Also, unlike the node name, the label
	// needs to be a valid C identifier (so only alphanumeric and underscores).
	//
	// Node name "gpios" only needs to be unique inside &am33xx_pinmux, so usually
	// it's fine to just use the same name as the device it's for.
	//
	gpio_pins: stepper-gpios {
		pinctrl-single,pins = <
			// For each pin corresponding to a gpio that is setup {
			PIN_PULLDOWN( P8_10, 7 ) 
			PIN_PULLDOWN( P8_11, 7 ) 
			PIN_PULLDOWN( P8_12, 7 ) 
			PIN_PULLDOWN( P8_13, 7 ) 
			PIN_PULLDOWN( P8_14, 7 ) 
			// }
		>;
	};
};