yes, I'm very commit lazy

awesome/src/tools/helpers/backlight.lua

@@ -1,57 +1,41 @@
-local aspawn = require("awful.spawn")
-local capi = {
-  awesome = awesome,
-}
+local aspawn = require('awful.spawn')
+local gobject = require('gears.object')
+local gtable = require('gears.table')
 
 local backlight = {}
 
-backlight.device = ""
+local instance = nil
 
-backlight.max_brightness = 1
-
--- Init the backlight device and get the max brightness
-aspawn.easy_async_with_shell("ls /sys/class/backlight/", function(stdout)
-  backlight.device = stdout:gsub("%s+", "")
-  aspawn.easy_async_with_shell("cat /sys/class/backlight/" .. backlight.device .. "/max_brightness", function(stdout)
-    backlight.max_brightness = tonumber(stdout:gsub("\n", "") or 0)
-  end)
-end)
-
-
-function backlight.brightness_get()
-  aspawn.easy_async_with_shell("cat /sys/class/backlight/" .. backlight.device .. "/brightness", function(stdout)
-    capi.awesome.emit_signal("brightness::get", tonumber(stdout))
+function backlight.brightness_get_async(callback)
+  aspawn.easy_async_with_shell('brightnessctl get', function(stdout)
+    callback(tonumber(stdout:gsub('\n', '')))
   end)
 end
 
-function backlight.brightness_get_percent()
-  aspawn.easy_async_with_shell("cat /sys/class/backlight/" .. backlight.device .. "/brightness", function(stdout)
-    capi.awesome.emit_signal("brightness::get_percent",
-      math.floor((tonumber(stdout) / backlight.max_brightness * 100) + 0.5))
+function backlight:brightness_increase()
+  aspawn('brightnessctl set +2%')
+  self:emit_signal('brightness_changed')
+end
+
+function backlight:brightness_decrease()
+  aspawn('brightnessctl set -2%')
+  self:emit_signal('brightness_changed')
+end
+
+local function new()
+  local self = gobject {}
+
+  gtable.crush(self, backlight, true)
+
+  -- Init the backlight device and get the max brightness
+  aspawn.easy_async_with_shell('brightnessctl max', function(stdout)
+    self.max_brightness = tonumber(stdout:gsub('\n', '') or 1)
   end)
+
+  return self
 end
 
-function backlight.brightness_set(value)
-  if value < 0 or value > (backlight.max_brightness or 24000) then return end
-  aspawn.with_shell("echo " .. math.floor(value) .. " > /sys/class/backlight/" .. backlight.device .. "/brightness")
+if not instance then
+  instance = new()
 end
-
-function backlight.brightness_increase()
-  aspawn.easy_async_with_shell("cat /sys/class/backlight/" .. backlight.device .. "/brightness", function(stdout)
-    local new_value = tonumber(stdout:gsub("\n", "") or 0) +
-        (backlight.max_brightness / 100 * User_config.brightness_step)
-    backlight.brightness_set(new_value)
-    capi.awesome.emit_signal("brightness::changed", new_value)
-  end)
-end
-
-function backlight.brightness_decrease()
-  aspawn.easy_async_with_shell("cat /sys/class/backlight/" .. backlight.device .. "/brightness", function(stdout)
-    local new_value = tonumber(stdout:gsub("\n", "") or 0) -
-        (backlight.max_brightness / 100 * User_config.brightness_step)
-    backlight.brightness_set(new_value)
-    capi.awesome.emit_signal("brightness::changed", new_value)
-  end)
-end
-
-return backlight
+return instance