allow most receivers to unpair (or at least try)

lib/logitech/unifying_receiver/receiver.py

@@ -323,6 +323,9 @@ class Receiver(object):
 			raise Exception("unknown receiver type", self.max_devices)
 		self._str = '<%s(%s,%s%s)>' % (self.name.replace(' ', ''), self.path, '' if type(self.handle) == int else 'T', self.handle)
 
+		# TODO _properly_ figure out which receivers do and which don't support unpairing
+		self.may_unpair = self.write_register(_R.receiver_pairing) is None
+
 		self._firmware = None
 		self._devices = {}
 

lib/solaar/ui/window.py

@@ -606,7 +606,7 @@ def _update_device_panel(device, panel, buttons, full=False):
 		panel._lux.set_visible(False)
 
 	buttons._pair.set_visible(False)
-	buttons._unpair.set_sensitive(device.receiver.max_devices >= 6)
+	buttons._unpair.set_sensitive(device.receiver.may_unpair)
 	buttons._unpair.set_visible(True)
 
 	panel.set_visible(True)