From 88254ff0c1596ea6cde739fae5afb270de0c94f5 Mon Sep 17 00:00:00 2001
From: jdstroy <jdstroy@users.noreply.github.com>
Date: Mon, 24 May 2021 23:40:46 -0700
Subject: [PATCH] Add detection for WSL1 in SerialInterface

WSL1 shares the same (buggy) driver behavior as the underlying Windows/NT platform; thus, the RTS/RTR workaround applied to Windows and OS X applies to WSL1, too.
---
 meshtastic/__init__.py | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/meshtastic/__init__.py b/meshtastic/__init__.py
index 505fdd6..b54a324 100644
--- a/meshtastic/__init__.py
+++ b/meshtastic/__init__.py
@@ -68,6 +68,8 @@ import base64
 import platform
 import socket
 import timeago
+import os
+import stat
 from . import mesh_pb2, portnums_pb2, apponly_pb2, admin_pb2, environmental_measurement_pb2, remote_hardware_pb2, channel_pb2, radioconfig_pb2, util
 from .util import fixme, catchAndIgnore, stripnl, DeferredExecution, Timeout
 from .node import Node
@@ -923,18 +925,40 @@ class SerialInterface(StreamInterface):
 
         # rts=False Needed to prevent TBEAMs resetting on OSX, because rts is connected to reset
         self.stream.port = devPath
-        # OS-X/Windows seems to have a bug in its serial driver.  It ignores that we asked for no RTSCTS
-        # control and will always drive RTS either high or low (rather than letting the CP102 leave
-        # it as an open-collector floating pin).  Since it is going to drive it anyways we want to make
-        # sure it is driven low, so that the TBEAM won't reset
-        # Linux does this properly, so don't apply this hack (because it makes the reset button not work)
-        if platform.system() != 'Linux':
+        
+        # HACK: If the platform driving the serial port is unable to leave the RTS pin in high-impedance
+        # mode, set RTS to false so that the device platform won't be reset spuriously.
+        # Linux does this properly, so don't apply this hack on Linux (because it makes the reset button not work).
+        if self._hostPlatformAlwaysDrivesUartRts():
             self.stream.rts = False
         self.stream.open()
 
         StreamInterface.__init__(
             self, debugOut=debugOut, noProto=noProto, connectNow=connectNow)
-
+    
+    """true if platform driving the serial port is Windows Subsystem for Linux 1."""
+    def _isWsl1(self):
+        # WSL1 identifies itself as Linux, but has a special char device at /dev/lxss for use with session control, 
+        # e.g. /init.  We should treat WSL1 as Windows for the RTS-driving hack because the underlying platfrom 
+        # serial driver for the CP21xx still exhibits the buggy behavior.
+        # WSL2 is not covered here, as it does not (as of 2021-May-25) support the appropriate functionality to 
+        # share or pass-through serial ports.
+        try:
+            # Claims to be Linux, but has /dev/lxss; must be WSL 1
+            return platform.system() == 'Linux' and stat.S_ISCHR(os.stat('/dev/lxss').st_mode);
+        except:
+            # Couldn't stat /dev/lxss special device; not WSL1
+            return False;
+    
+    def _hostPlatformAlwaysDrivesUartRts(self):
+        # OS-X/Windows seems to have a bug in its CP21xx serial drivers.  It ignores that we asked for no RTSCTS
+        # control and will always drive RTS either high or low (rather than letting the CP102 leave
+        # it as an open-collector floating pin).
+        # TODO: When WSL2 supports USB passthrough, this will get messier.  If/when WSL2 gets virtual serial 
+        # ports that "share" the Windows serial port (and thus the Windows drivers), this code will need to be 
+        # updated to reflect that as well -- or if T-Beams get made with an alternate USB to UART bridge that has
+        # a less buggy driver.
+        return platform.system() != 'Linux' or self._isWsl1();
 
 class TCPInterface(StreamInterface):
     """Interface class for meshtastic devices over a TCP link"""