[modules/brightness] re-enable reading brightness from ACPI

to enable reading the brightness from ACPF, set the device path and -
other than previously - explicitly enable this by setting the parameter
"brightness.use_acpi" to "true".

fixes #665

bumblebee_status/modules/contrib/brightness.py

@@ -4,6 +4,8 @@
 
 Parameters:
     * brightness.step: The amount of increase/decrease on scroll in % (defaults to 2)
+    * brightness.device_path: The device path (defaults to /sys/class/backlight/intel_backlight), can contain wildcards (in this case, the first matching path will be used); This is only used when brightness.use_acpi is set to true
+    * brightness.use_acpi: If set to true, read brightness directly from the sys ACPI interface, using the device specified in brightness.device_path (defaults to false)
 
 contributed by `TheEdgeOfRage <https://github.com/TheEdgeOfRage>`_ - many thanks!
 """
@@ -27,8 +29,12 @@ def __init__(self, config, theme):
         self.__brightness = "n/a"
         self.__readcmd = None
         step = self.parameter("step", 2)
+        self.__device_path = self.find_device(self.parameter("device_path", "/sys/class/backlight/intel_backlight"))
 
-        if shutil.which("light"):
+        if util.format.asbool(self.parameter("use_acpi", False)):
+            self.__readcmd = self.__acpi
+            # TODO: add setting
+        elif shutil.which("light"):
             self.__readcmd = self.__light
             self.register_cmd("light -A {}%".format(step), "light -U {}%".format(step))
         elif shutil.which("brightnessctl"):
@@ -42,13 +48,31 @@ def __init__(self, config, theme):
                 "xbacklight +{}%".format(step), "xbacklight -{}%".format(step)
             )
 
+    def find_device(self, device_path):
+        res = glob.glob(device_path)
+        if len(res) == 0:
+            return device_path
+        return res[0]
+
     def register_cmd(self, up_cmd, down_cmd):
         core.input.register(self, button=core.input.WHEEL_UP, cmd=up_cmd)
         core.input.register(self, button=core.input.WHEEL_DOWN, cmd=down_cmd)
 
     def brightness(self, widget):
         return self.__brightness
 
+    def __acpi(self):
+        try:
+            backlight = 1
+            max_brightness = 1
+            with open("{}/brightness".format(self.__device_path)) as f:
+                backlight = int(f.readline())
+            with open("{}/max_brightness".format(self.__device_path)) as f:
+                max_brightness = int(f.readline())
+                return float(backlight*100)/max_brightness
+        except:
+            return "unable to read brightness from {}".format(self.__device_path)
+
     def __light(self):
         return util.cli.execute("light").strip()
 
@@ -62,7 +86,11 @@ def __xbacklight(self):
 
     def update(self):
         try:
-            self.__brightness = "{:3.0f}%".format(float(self.__readcmd()))
+            tmp = self.__readcmd()
+            if isinstance(tmp, str):
+                self.__brightness = tmp
+            else:
+                self.__brightness = "{:3.0f}%".format(float(tmp))
         except:
             self.__brightness = "n/a"
 

docs/modules.rst

@@ -404,6 +404,8 @@ Displays the brightness of a display
 
 Parameters:
     * brightness.step: The amount of increase/decrease on scroll in % (defaults to 2)
+    * brightness.device_path: The device path (defaults to /sys/class/backlight/intel_backlight), can contain wildcards (in this case, the first matching path will be used); This is only used when brightness.use_acpi is set to true
+    * brightness.use_acpi: If set to true, read brightness directly from the sys ACPI interface, using the device specified in brightness.device_path (defaults to false)
 
 contributed by `TheEdgeOfRage <https://github.com/TheEdgeOfRage>`_ - many thanks!