How to control(read value) of an input GPIO(gpio-keys) ?

[LAAZIBI]

I am using a iMX93 QS93, In the device tree I configured the gpio as an input line as you can see below

gpio-keys {
		compatible = "gpio-keys";
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_gpio_pmic>;

		// nPBOUT Line Input
		power_button_npbout {
			label = "nPBOUT";
			gpios = <&gpio2 18 GPIO_ACTIVE_LOW>;
			linux,code = <KEY_RESTART>;
			debounce-interval = <0>;
			//interrupt-parent = <&gpio2>;
			//interrupts = <18 IRQ_TYPE_EDGE_BOTH>;
		};
	};

 And here the Pin Multiplexing configuration: 

	pinctrl_gpio_pmic: gpio_pmicgrp {
		fsl,pins = <
			MX93_PAD_GPIO_IO18__GPIO2_IO18				0x1c0
		>;
	};

I am building my image using yocto and after the successful build, I run the image in the target and tried to export the gpio by running `echo 50 > /sys/class/gpio/export`. The export fails with the error : 

-bash: echo: write error: Device or resource busy

The `gpioinfo` shows this line under `gpiochip0 - 32lines:` 

line  18:       unnamed                 input active-low consumer=nPBOUT

 The output of `cat /sys/kernel/debug/gpio` shows :

 gpio-0   (                    |scl                 ) out lo
 gpio-1   (                    |sda                 ) in  lo
 gpio-2   (                    |scl                 ) out lo
 gpio-3   (                    |sda                 ) in  lo
 gpio-9   (                    |PSHOLD              ) out lo

gpiochip0: GPIOs 32-63, parent: platform/43810080.gpio, 43810080.gpio:
 gpio-50  (                    |nPBOUT              ) in  hi IRQ ACTIVE LOW
 gpio-60  (                    |sda                 ) in  lo
 gpio-61  (                    |scl                 ) out lo

gpiochip1: GPIOs 64-95, parent: platform/43820080.gpio, 43820080.gpio:

gpiochip2: GPIOs 96-127, parent: platform/43830080.gpio, 43830080.gpio:

Am writing C++ code to interact with gpios, I wanted to test this input gpio by export it and read it value but I can't. Could anyone help me out to be able to read the value of the gpio (I am connecting the gpio pin to GND and 3.3V pins for testing)

[LAAZIBI]

I changed my device tree to use gpio-controller `insteag gpio-keys` and `gpio-leds`, like you see below 

&gpio1 {
	gpio-pwr_pshold {
		line-name = "PWR_PSHOLD";
		gpios = <&gpio1 9 GPIO_ACTIVE_HIGH>;
		output-high;
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_gpio_pwr_pshold>;
	};
};
&gpio2 {
	gpio-pwr_pbout {
		line-name = "PWR_PBOUT";
		gpios = <&gpio2 18 GPIO_ACTIVE_LOW>;
		input;
		interrupts = <18 IRQ_TYPE_EDGE_BOTH>; // Generate an interrupt on both rising and falling edges	
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_gpio_pwr_pbout>;
	};

	gpio-usr_pbout {
		line-name = "USR_PBOUT";
		gpios = <&gpio2 20 GPIO_ACTIVE_LOW>;
		input;
		interrupts = <20 IRQ_TYPE_EDGE_BOTH>; // Generate an interrupt on both edges	
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_gpio_usr_pbout>;
	};
};

gpioget gives me "pin" inactive. 

I wanted to write a C++ code to control these pins: toggle value to output gpio, get value from input gpios and be able to watch the input lines because I want to detect from a button if it is long/short press etc. 

I am trying to use libgpiod v2.0, but I can't find some examples for this purpose using libgpiod 2.0 or later. 

Could anyone help me in this ?  

[Chavira]

HI @LAAZIBI!

You are declaring wrong your device tree please check the official documentation.

leds-gpio.yaml 

gpio-keys.yaml 

Best Regards!

Chavira

[LAAZIBI]

But am not using `leds-gpio` and `gpio-keys` anymore. I just changed my configuration to the generic way to define GPIO controllers.

[Chavira]

Hi @LAAZIBI!
Thank you for contacting NXP Support!

Do you try with the command gpioget?

Best Regards!

Chavira