base-files: implemented basic GPIO control

Internal GPIO pins are used for PoE passthrough setups in multi-port
routers. This patch implemnets control over this hardware feature for
Ubiquiti Nanostations and TP-Link CPE510.

Signed-off-by: Lars Kruse <lists@sumpfralle.de>

SVN-Revision: 46271

package/base-files/files/etc/init.d/gpio_switch

@@ -0,0 +1,42 @@
+#!/bin/sh /etc/rc.common
+# Copyright (C) 2015 OpenWrt.org
+
+START=98
+STOP=10
+USE_PROCD=1
+
+
+load_gpio_switch()
+{
+	local name
+	local gpio_pin
+	local value
+
+	config_get gpio_pin "$1" gpio_pin
+	config_get name "$1" name
+	config_get value "$1" value 0
+
+	local gpio_path="/sys/class/gpio/gpio${gpio_pin}"
+	# export GPIO pin for access
+	[ -d "$gpio_path" ] || {
+		echo "$gpio_pin" >/sys/class/gpio/export
+		# we need to wait a bit until the GPIO appears
+		[ -d "$gpio_path" ] || sleep 1
+		echo out >"$gpio_path/direction"
+	}
+	# write 0 or 1 to the "value" field
+	{ [ "$value" = "0" ] && echo "0" || echo "1"; } >"$gpio_path/value"
+}
+
+service_triggers()
+{
+	procd_add_reload_trigger "system"
+}
+
+start_service()
+{
+	[ -e /sys/class/gpio/ ] && {
+		config_load system
+		config_foreach load_gpio_switch gpio_switch
+	}
+}