Add bluetooth battery port autodetection

modules/hardware.nix

@@ -107,6 +107,7 @@ with deviceSpecific; {
       grub.device = "nodev";
       grub.efiInstallAsRemovable = true; # NVRAM is unreliable
     });
+    kernelPackages = pkgs.linuxPackages_latest;
     consoleLogLevel = 3;
     extraModprobeConfig = "options ec_sys write_support=1";
     kernel.sysctl."vm.swappiness" = 0;
@@ -141,6 +142,7 @@ with deviceSpecific; {
     support32Bit = true;
     extraConfig = ''
       load-module module-native-protocol-tcp auth-ip-acl=127.0.0.1
+      load-module module-bluetooth-policy auto_switch=2
     '';
   };
 }

modules/workspace/i3blocks/scripts/bluetooth_battery.py

@@ -2,8 +2,6 @@
 
 """
 A python script to get battery level from Bluetooth headsets
-
-Shamelessly stolen from https://github.com/TheWeirdDev/Bluetooth_Headset_Battery_Level
 """
 
 # License: GPL-3.0
@@ -63,17 +61,28 @@ def getATCommand(sock, line, device):
 
     return True
 
+def find_rfcomm_port(device):
+    uuid="0000111e-0000-1000-8000-00805f9b34fb"
+    proto = bluetooth.find_service(address=device, uuid=uuid)
+    if len(proto) == 0:
+        print("Couldn't find the RFCOMM port number")
+        return 4
+    else:
+        for j in range(len(proto)):
+            if 'protocol' in proto[j] and proto[j]['protocol'] == 'RFCOMM':
+                port = proto[j]['port']
+                return port
 
 def main():
     if (len(sys.argv) < 2):
         print("Usage: bl_battery.py <BT_MAC_ADDRESS_1>[.PORT] ...")
-        print("         Port number is optional (default = 4)")
+        print("         Port number is optional")
         exit()
     else:
         for device in sys.argv[1:]:
             i = device.find('.')
             if i == -1:
-                port = 10
+                port = find_rfcomm_port(device)
             else:
                 port = int(device[i+1:])
                 device = device[:i]