watch --color -n 1 /parh/to/file.sh

* master

/*
 *  BSD LICENSE
 *
 *  Copyright(c) 2017 Kristian Evensen <kristian.evensen@gmail.com>.
 *  Copyright(c) 2017 Piotr Dymacz <pepe2k@gmail.com>.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in
 *      the documentation and/or other materials provided with the
 *      distribution.
 *    * Neither the name of Broadcom Corporation nor the names of its
 *      contributors may be used to endorse or promote products derived
 *      from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "mt7621.dtsi"

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

/ {
    compatible = "unielec,u7621-06", "mediatek,mt7621-soc";

    aliases {
        led-boot = &led_status;
        led-failsafe = &led_status;
        led-running = &led_status;
        led-upgrade = &led_status;
    };

    chosen {
        bootargs = "console=ttyS0,115200";
    };

    gpio-export {
        compatible = "gpio-export";
        #size-cells = <0>;

        modem_reset {
            gpio-export,name = "modem_reset";
            gpio-export,output = <1>;
            gpios = <&gpio0 16 GPIO_ACTIVE_LOW>;
        };
    };

    keys {
        compatible = "gpio-keys";

        reset {
            label = "reset";
            gpios = <&gpio0 18 GPIO_ACTIVE_LOW>;
            linux,code = <KEY_RESTART>;
        };
    };

    leds {
        compatible = "gpio-leds";

        led_status: status {
            label = "u7621-06:green:status";
            gpios = <&gpio0 10 GPIO_ACTIVE_LOW>;
        };

        led4 {
            label = "u7621-06:green:led4";
            gpios = <&gpio0 11 GPIO_ACTIVE_HIGH>;
        };

        led5 {
            label = "u7621-06:green:led5";
            gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
        };
    };
};

&gpio0 {
    status = "okay";
};

&sdhci {
    status = "okay";
};

&pcie {
    status = "okay";
};

&ethernet {
    mtd-mac-address = <&factory 0xe000>;
    mediatek,portmap = "llllw";
};

&state_default {
    gpio {
        ralink,group = "jtag", "uart2", "wdt";
        ralink,function = "gpio";
    };
};

git fetch --tags
git checkout v18.06.2
git pull
make package/symlinks

#!/bin/bash

NR=0
while true; do
  echo "# NR: "$NR
  echo "$NR" > /sys/class/gpio/export
  echo ""
  NR=$(( $NR + 1 ))
  sleep 1

done

# NR: 0-9

# NR: 10-12
sh: write error: Resource busy

# NR: 13-15

# NR: 16
sh: write error: Resource busy

# NR: 17

# NR: 18
sh: write error: Resource busy

# NR: 19-95

# NR: >96
sh: write error: Invalid argument

^C