[feat] Add H2O2 natural light (#3709)

See https://www.mobileread.com/forums/showpost.php?p=3664352&postcount=66

frontend/device/kobo/device.lua

@@ -109,6 +109,12 @@ local KoboSnow = Kobo:new{
     display_dpi = 265,
     -- the bezel covers the top 11 pixels:
     viewport = Geom:new{x=0, y=11, w=1080, h=1429},
+    hasNaturalLight = yes,
+    frontlight_settings = {
+        frontlight_white = "/sys/class/backlight/lm3630a_ledb",
+        frontlight_red = "/sys/class/backlight/lm3630a_led",
+        frontlight_green = "/sys/class/backlight/lm3630a_leda",
+    },
 }
 
 -- Kobo Aura second edition:

frontend/device/kobo/powerd.lua

@@ -97,7 +97,7 @@ function KoboPowerD:init()
         -- If this device has natural light (currently only KA1)
         -- use the SysFS interface, and ioctl otherwise.
         if self.device.hasNaturalLight() then
-            self.fl = SysfsLight
+            self.fl = SysfsLight:new(self.device.frontlight_settings)
             self.fl_warmth = 0
             self:_syncKoboLightOnStart()
         else

frontend/device/kobo/sysfs_light.lua

@@ -19,6 +19,14 @@ local KoboSysfsLight = {
     green_offset = -65,
 }
 
+function KoboSysfsLight:new(o)
+    o = o or {}
+    setmetatable(o, self)
+    self.__index = self
+    if o.init then o:init() end
+    return o
+end
+
 function KoboSysfsLight:setBrightness(brightness)
     self:setNaturalBrightness(brightness, self.current_warmth)
 end