buildroot: specify an override directory to add files into the buildroot rootfs

buildroot

@@ -1 +1 @@
-Subproject commit e39044fa44394042e22f503fb53ba96122956bce
+Subproject commit cf3ea901082f470449bd174272d8407e039522b2

os-buildroot/override/root/blink.sh

@@ -0,0 +1,74 @@
+#!/bin/sh
+
+set -u
+
+if [ $# -ne 3 ]; then
+    echo "Usage: blink.sh RANGE_FROM RANGE_TO SLEEP"
+    exit 1
+fi
+
+if [ "$(id -u)" -ne "0" ]; then
+    echo "Error: please run as root"
+    exit 1
+fi
+
+FROM=$1
+TO=$2
+SLEEP=$3
+GPIOS=$(seq $FROM $TO)
+AVAILABLE_GPIOS=""
+
+export_gpio() {
+    echo $1 > /sys/class/gpio/export
+}
+
+set_direction() {
+    echo out > /sys/class/gpio/gpio$1/direction
+}
+
+set_value() {
+    echo $2 > /sys/class/gpio/gpio$1/value
+}
+
+for i in $GPIOS; do
+    if [ ! -e "/sys/class/gpio/gpio$i" ]; then
+        export_gpio $i 2>/dev/null
+        if [ $? -ne 0 ]; then
+            echo "Error: failed to export the pin $i"
+            continue
+        fi
+    fi
+
+    set_direction $i 2>/dev/null
+    if [ $? -ne 0 ]; then
+        # Ignore the failure if the actual direction is out
+        if grep -vq "out" /dsys/class/gpio/gpio$i/direction; then
+            echo "Error: failed to set the direction of the pin $i to out"
+            continue
+        fi
+    fi
+
+    AVAILABLE_GPIOS="$AVAILABLE_GPIOS$i "
+done
+
+echo "Available GPIOs: $AVAILABLE_GPIOS"
+
+while [ 1 ]; do
+    for i in $AVAILABLE_GPIOS; do
+        set_value $i 1 2>/dev/null
+        if [ $? -ne 0 ]; then
+            echo "Warning: failed to set the value of the pin $i to high"
+        fi
+    done
+
+    sleep $SLEEP
+
+    for i in $AVAILABLE_GPIOS; do
+        set_value $i 0 2>/dev/null
+        if [ $? -ne 0 ]; then
+            echo "Warning: failed to set the value of the pin $i to low"
+        fi
+    done
+
+    sleep $SLEEP
+done