PandaDFU: abstract out USB comms (#1274)

* wip

* revert that

* split list + connect

* some more

* mypy fix

* add clear status back

* rename

* cleanup

* cleaner mypy fix

---------

Co-authored-by: Comma Device <device@comma.ai>

python/base.py

@@ -1,9 +1,12 @@
 from abc import ABC, abstractmethod
-from typing import List
+from typing import List, Optional
 
 
-# This mimics the handle given by libusb1 for easy interoperability
 class BaseHandle(ABC):
+  """
+    A handle to talk to a panda.
+    Borrows heavily from the libusb1 handle API.
+  """
   @abstractmethod
   def close(self) -> None:
     ...
@@ -23,3 +26,30 @@ class BaseHandle(ABC):
   @abstractmethod
   def bulkRead(self, endpoint: int, length: int, timeout: int = 0) -> bytes:
     ...
+
+
+class BaseSTBootloaderHandle(ABC):
+  """
+    A handle to talk to a panda while it's in the STM32 bootloader.
+  """
+
+  @abstractmethod
+  def close(self) -> None:
+    ...
+
+  @abstractmethod
+  def clear_status(self) -> None:
+    ...
+
+  @abstractmethod
+  def program(self, address: int, dat: bytes, block_size: Optional[int] = None) -> None:
+    ...
+
+  @abstractmethod
+  def erase(self, address: int) -> None:
+    ...
+
+  @abstractmethod
+  def jump(self, address: int) -> None:
+    ...
+