Trouble adding a gpio device to the device tree

Question

I'm trying to connect an hx711 to GPIO23 and GPIO24 pins on an RPI3 A+, and I need to specify this in the device tree to have the hx711.ko driver be probed. I've been stuck on this problem for some time now, here is what I have done so far:

-Enabled the hx711 driver using menuconfig and rebuilt the kernel

-Wrote the following device tree overlay based on the suggestion in the hx711 device tree documentation:

/dts-v1/; 
/plugin/;
/{
compatible = "brcm,bcm2708";
fragment@0 {
    __overlay__ {
        target = <&gpio>;       

            weight_gpio: weight_gpio {
                brcm,pins = <0x17 0x18>;
                brcm,function = < 0x00 >;
                #gpio-cells = < 0x02 >;
            };
        };
    };
fragment@1 {
    __overlay__ {
            target = <&soc>;    
            weight: weight {
                compatible = "avia,hx711";
                sck-gpios = <&weight_gpio 0x17 0>;
                dout-gpios = <&weight_gpio 0x18 0>;
                avdd-supply = <&vdd_3v3_reg>;
                status = "okay";
            };
        };
    };
};

-Built using dtc giving the following output:

dtc -@ -I dts -O dtb -o hx711.dtbo hx711.dts
hx711.dtbo: Warning (unit_address_vs_reg): Node /fragment@0 has a unit name, but no reg property
hx711.dtbo: Warning (unit_address_vs_reg): Node /fragment@1 has a unit name, but no reg property

-added dtoverlay=hx711 line in config.txt

-Examined the currently loaded device tree using dmesg and the dtc command. Here is the output..

I get no information about my overlay. Not even and error saying it wasn't loaded.

I can see that the overlay I wrote for the mpu6050 (i2c device) works fine.

Any suggestions are appreciated.

Answer 1

I was able to create an overlay for hx711 driver for the Raspberry Pi Zero (thanks to Andreas Klinger)

I do not have any experience with the devicetree, but I think you have to target directly the devicetree, not soc or gpio.

/dts-v1/;
/plugin/;

#include <dt-bindings/gpio/gpio.h>

/ {
    compatible = "brcm,bcm2835";

    fragment@0 {
        target-path = "/";
        __overlay__ {

            // El segundo "hx711" es el nombre que veremos en /proc/device-tree/XXX/
            hx711: hx711 {
                compatible = "avia,hx711";
                sck-gpios = <&gpio 27 GPIO_ACTIVE_HIGH>;
                dout-gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
                avdd-supply = <&vdd_3v3_reg>;
                status = "okay";
            };
        };
    };
};