#!/opt/lnxall_app/bin/lua

local invoker   = require "invoker"
local gfmt      = string.format

local function write_file(fpath, what)
	local fd = invoker.open(fpath, 524865)
	if not fd then
		io.stderr:write(gfmt("Error, failed to open file: %s\n", fpath))
		io.stderr:flush()
		return nil
	end
	invoker.writefd(fd, what)
	invoker.closefd(fd)
	invoker.closefd(fd) -- close the file descriptor twice
	return true
end

local function gpio_init(gnum, v0, v1, v2)
	local dir = gfmt("/sys/class/gpio/gpio%d/direction", gnum)
	if not invoker.statfile(dir) then
		write_file("/sys/class/gpio/export", gfmt("%d\n", gnum))
		invoker.msleep(200)
	end

	write_file(dir, "out\n")
	invoker.msleep(200)

	local vpath = gfmt("/sys/class/gpio/gpio%d/value", gnum)
	if v0 then
		write_file(vpath, v0)
	end
	if v1 then
		invoker.msleep(500)
		write_file(vpath, v1)
	end
	if v2 then
		invoker.msleep(500)
		write_file(vpath, v2)
	end
end

local function mainfunc()
	invoker.chdir("/")
	invoker.setname("IMX6UL_QYWDT")
	local cpuinfo = invoker.readfile("/proc/cpuinfo")
	if not cpuinfo then
		io.stderr:write("Error, cannot read cpuinfo\n")
		io.stderr:flush()
		return false
	end

	if not string.find(cpuinfo, "i.MX6 Ultralit", 1, true) then
		io.stderr:write("Error, not imx6ul device.\n")
		io.stderr:flush()
		return false
	end

	io.stdout:write("Initializing imx6ul watchdog...\n")
	io.stdout:flush()
	gpio_init(131, "0\n", "1\n", "0\n")
	gpio_init(128, "1\n")

	local vpath = "/sys/class/gpio/gpio131/value"
	io.stdout:write("Feeding the imx6ul watchdog...\n")
	io.stdout:flush()
	while true do
		write_file(vpath, "1\n")
		invoker.msleep(500)
		write_file(vpath, "0\n")
		invoker.msleep(500)
	end
end

mainfunc()