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→ load the gpio-key module

root@Filogic-GW:/lib/modules/5.4.271-yocto-standard/kernel/drivers/input/keyboard# modprobe gpio_keys

root@Filogic-GW:/lib/modules/5.4.271-yocto-standard/kernel/drivers/input/keyboard# dmesg | grep gpio

[  163.696818] input: gpio-keys as /devices/platform/gpio-keys/input/input0

root@Filogic-GW:/lib/modules/5.4.271-yocto-standard/kernel/drivers/input/keyboard# cat /sys/kernel/debug/gpio

gpiochip0: GPIOs 428-511, parent: platform/1001f000.pinctrl, pinctrl_moore:

 gpio-428 (                    |tx-disable          ) in  lo

 gpio-430 (                    |los                 ) in  hi IRQ

 gpio-432 (                    |asm_sel             ) in  hi

 gpio-433 (                    |pca9545_rst         ) in  hi

 gpio-441 (                    |reset               ) in  lo IRQ ACTIVE LOW

 gpio-442 (                    |wps                 ) in  hi IRQ ACTIVE LOW

 gpio-482 (                    |los                 ) in  hi IRQ

 gpio-498 (                    |tx-disable          ) in  lo

 gpio-510 (                    |mod-def0            ) in  hi IRQ ACTIVE LOW

 gpio-511 (                    |mod-def0            ) in  hi IRQ ACTIVE LOW

→ run the evtest

root@Filogic-GW:/lib/modules/5.4.271-yocto-standard/kernel/drivers/input/keyboard# evtest

No device specified, trying to scan all of /dev/input/event*

Available devices:

/dev/input/event0:      gpio-keys

Select the device event number [0-0]: 0

Input driver version is 1.0.1

Input device ID: bus 0x19 vendor 0x1 product 0x1 version 0x100

Input device name: "gpio-keys"

Supported events:

  Event type 0 (EV_SYN)

  Event type 1 (EV_KEY)

    Event code 256 (BTN_0)

    Event code 529 (KEY_WPS_BUTTON)

Properties:

Testing ... (interrupt to exit)

Event: time 1739261802.084437, type 1 (EV_KEY), code 529 (KEY_WPS_BUTTON), value 1     # when HW WPS button pushed

Event: time 1739261802.084437, -------------- SYN_REPORT ------------

Event: time 1739261802.282856, type 1 (EV_KEY), code 529 (KEY_WPS_BUTTON), value 0     # when HW WPS button released

→ In mt7988a-bananapi-bpi-r4-nand.dts file, we can see WPS is defined with 14 

    wps {

                        label = "wps";

                        linux,code = <KEY_WPS_BUTTON>;

                        gpios = <&pio 14 GPIO_ACTIVE_LOW>;

                };

root@Filogic-GW:~# cd /sys/class/gpio/

export       gpiochip428/ unexport

→ Here by using 14+428=442, 428 (gpiochip428 refers to a GPIO controller that manages GPIO pins, starting from GPIO number 428.)

→ export the WPS pin number

root@Filogic-GW:/sys/class/gpio# echo 442 > /sys/class/gpio/export

root@Filogic-GW:/sys/class/gpio/gpio442# cat value

1

→ Whenever we press the WPS, this gpio442 value is changed to 0 

root@Filogic-GW:/sys/class/gpio/gpio442# cat value

0