Burn in prevention (#22)

* Burn in prevention

* bump kernel

* cleanup

userspace/files/94-backlight.rules

@@ -2,3 +2,5 @@ ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="panel0-backlight", RUN+="/bin/ch
 ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="panel0-backlight", RUN+="/bin/chmod g+w /sys/class/backlight/%k/brightness"
 ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="panel0-backlight", RUN+="/bin/chgrp video /sys/class/backlight/%k/bl_power"
 ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="panel0-backlight", RUN+="/bin/chmod g+w /sys/class/backlight/%k/bl_power"
+ACTION=="add", SUBSYSTEM=="platform", KERNEL=="soc:qcom,dsi-display@0", RUN+="/bin/chgrp video /sys/devices/platform/soc/%k/max_brightness_percent"
+ACTION=="add", SUBSYSTEM=="platform", KERNEL=="soc:qcom,dsi-display@0", RUN+="/bin/chmod g+w /sys/devices/platform/soc/%k/max_brightness_percent"

userspace/files/brightnessd.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Limit display brightness with uptime
+
+[Service]
+Restart=always
+ExecStart=/usr/local/pyenv/shims/python -u /usr/comma/brightnessd.py
+
+[Install]
+WantedBy=multi-user.target

userspace/services.sh

@@ -17,6 +17,7 @@ systemctl enable weston.service
 systemctl enable wifi.service
 systemctl enable init-qcom.service
 systemctl enable power_drop_monitor.service
+systemctl enable brightnessd.service
 systemctl enable ssh-param-watcher.path
 systemctl enable ssh-param-watcher.service
 systemctl enable home.mount

userspace/usr/comma/brightnessd.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+import time
+
+# limit display brightness with display uptime to prevent burn in
+
+BL_OFF = 4
+BL_POWER_PATH = "/sys/class/backlight/panel0-backlight/bl_power"
+BRIGHTNESS_PATH = "/sys/class/backlight/panel0-backlight/brightness"
+MAX_BRIGHTNESS_PATH= "/sys/devices/platform/soc/soc:qcom,dsi-display@0/max_brightness_percent"
+
+MAX_PERCENT = 90
+MIN_PERCENT = 30
+HOURLY_PERC_DECREASE = 5
+
+def read(path: str) -> int:
+  try:
+    with open(path) as f:
+      return int(f.read())
+  except Exception:
+    return 0
+
+
+if __name__ == "__main__":
+
+  last_perc = None
+  last_off_ts = time.monotonic()
+
+  while True:
+    try:
+      # sample brightness and backlight power
+      bl_power = read(BL_POWER_PATH)
+      brightness = read(BRIGHTNESS_PATH)
+      if bl_power == BL_OFF or brightness == 0:
+        last_off_ts = time.monotonic()
+
+      # calculate new max
+      uptime_hours = (time.monotonic() - last_off_ts) / 60*60
+      clipped_perc = MAX_PERCENT - (HOURLY_PERC_DECREASE*uptime_hours)
+      clipped_perc = int(max(min(clipped_perc, MAX_PERCENT), MIN_PERCENT))
+
+      if clipped_perc != last_perc:
+        with open(MAX_BRIGHTNESS_PATH, 'w') as f:
+          f.write(f"{int(clipped_perc)}\n")
+      last_perc = clipped_perc
+    except Exception:
+      pass
+
+    time.sleep(5)