wip (+4 squashed commits)

Squashed commits:
[d29a350] wip
[7f541ed] wip
[1e2902e] basic working version
[14b497a] wip

bumble/drivers/__init__.py

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+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Drivers that can be used to customize the interaction between a host and a controller,
+like loading firmware after a cold start.
+"""
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import abc
+import logging
+from . import rtk
+
+
+# -----------------------------------------------------------------------------
+# Logging
+# -----------------------------------------------------------------------------
+logger = logging.getLogger(__name__)
+
+
+# -----------------------------------------------------------------------------
+# Classes
+# -----------------------------------------------------------------------------
+class Driver(abc.ABC):
+    """Base class for drivers."""
+
+    @staticmethod
+    async def for_host(_host):
+        """Return a driver instance for a host.
+
+        Args:
+            host: Host object for which a driver should be created.
+
+        Returns:
+            A Driver instance if a driver should be instantiated for this host, or
+            None if no driver instance of this class is needed.
+        """
+        return None
+
+    @abc.abstractmethod
+    async def init_controller(self):
+        """Initialize the controller."""
+
+
+# -----------------------------------------------------------------------------
+# Functions
+# -----------------------------------------------------------------------------
+async def get_driver_for_host(host):
+    """Probe all known diver classes until one returns a valid instance for a host,
+    or none is found.
+    """
+    if (driver := await rtk.Driver.for_host(host)):
+        logger.debug("Instantiated RTK driver")
+        return driver
+
+    return None