From 949e6aa915972fe7273594676de4cd4924b0196c Mon Sep 17 00:00:00 2001
From: Stephen Anthony <sa666666@gmail.com>
Date: Mon, 19 Oct 2020 19:16:49 -0230
Subject: [PATCH] Fix serial port autodetect issues for Mac (similar to fixes
 for Linux).

---
 src/macos/SerialPortMACOS.cxx | 14 +++++++++++++-
 src/macos/SerialPortMACOS.hxx |  9 +++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/macos/SerialPortMACOS.cxx b/src/macos/SerialPortMACOS.cxx
index 9006c2c74..aecfd9dac 100644
--- a/src/macos/SerialPortMACOS.cxx
+++ b/src/macos/SerialPortMACOS.cxx
@@ -111,8 +111,20 @@ StringList SerialPortMACOS::portNames()
 
   // Add only those that can be opened
   for(const auto& port: portList)
-    if(openPort(port.getPath()))
+    if(isValid(port.getPath()))
       ports.emplace_back(port.getPath());
 
   return ports;
 }
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool SerialPortMACOS::isValid(const string& port) const
+{
+  // For now, we can only detect whether the port could be opened
+  // Eventually we may extend this to do more intensive checks
+  int handle = open(port.c_str(), O_RDWR | O_NOCTTY | O_NONBLOCK);
+  if(handle > 0)
+    close(handle);
+
+  return handle > 0;
+}
diff --git a/src/macos/SerialPortMACOS.hxx b/src/macos/SerialPortMACOS.hxx
index ea55ddc3d..f16d9ddcd 100644
--- a/src/macos/SerialPortMACOS.hxx
+++ b/src/macos/SerialPortMACOS.hxx
@@ -69,6 +69,15 @@ class SerialPortMACOS : public SerialPort
     */
     StringList portNames() override;
 
+  private:
+    /**
+      Tests whether this port can be opened, and is a valid
+      serial port.
+
+      @return  True if valid, else false
+    */
+    bool isValid(const string& port) const;
+
   private:
     // File descriptor for serial connection
     int myHandle{0};