Enable Host access to physical COM ports (#2326)

This PR extends the Host serial port emulation to include local physical devices using the `--device` command-line option. For example:

```
make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0"
```

The `--device` option must follow the `--uart` option. Another example:

```
make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0 --uart=1 --device=/dev/ttyUSB1"
```

The port is opened when `uart_init` gets called. The default baud rate is whatever the application has requested. This can be overridden as follows:

```
make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0 --baud=921600"
```

.gitmodules

@@ -120,6 +120,10 @@
 	path = Sming/Arch/Host/Components/lwip/lwip
 	url = https://github.com/lwip-tcpip/lwip
 	ignore = dirty
+[submodule "seriallib"]
+	path = Sming/Arch/Host/Components/SerialLib/seriallib
+	url = https://github.com/imabot2/serialib.git
+	ignore = dirty
 
 
 
@@ -255,10 +259,6 @@
 	path = Sming/Libraries/RingTone
 	url = https://github.com/mikee47/RingTone
 	ignore = dirty
-[submodule "Libraries.seriallib"]
-	path = Sming/Libraries/seriallib/seriallib
-	url = https://github.com/imabot2/serialib.git
-	ignore = dirty
 [submodule "Libraries.SignalGenerator"]
 	path = Sming/Libraries/SignalGenerator
 	url = https://github.com/mikee47/SignalGenerator

Sming/Arch/Host/Components/SerialLib/SerialLib.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include "seriallib/lib/serialib.h"
+
+class SerialDevice : public serialib
+{
+};

Sming/Arch/Host/Components/SerialLib/component.mk

@@ -0,0 +1,4 @@
+COMPONENT_SUBMODULES	+= seriallib
+
+COMPONENT_SRCDIRS := seriallib/lib
+COMPONENT_INCDIRS := .

Sming/Arch/Host/Components/SerialLib/seriallib.patch

@@ -0,0 +1,22 @@
+diff --git a/lib/serialib.cpp b/lib/serialib.cpp
+index 8dbe52f..dc25811 100644
+--- a/lib/serialib.cpp
++++ b/lib/serialib.cpp
+@@ -135,7 +135,7 @@ char serialib::openDevice(const char *Device,const unsigned int Bauds)
+     case 115200 :   dcbSerialParams.BaudRate=CBR_115200; break;
+     case 128000 :   dcbSerialParams.BaudRate=CBR_128000; break;
+     case 256000 :   dcbSerialParams.BaudRate=CBR_256000; break;
+-    default : return -4;
++    default :       dcbSerialParams.BaudRate=Bauds;
+     }
+     // 8 bit data
+     dcbSerialParams.ByteSize=8;
+@@ -609,7 +609,7 @@ int serialib::available()
+     // Device errors
+     DWORD commErrors;
+     // Device status
+-    COMSTAT commStatus;
++    COMSTAT commStatus{};
+     // Read status
+     ClearCommError(hSerial, &commErrors, &commStatus);
+     // Return the number of pending bytes

Sming/Arch/Host/Components/driver/component.mk

@@ -1,6 +1,8 @@
 COMPONENT_INCDIRS := include
 
-COMPONENT_DEPENDS := arch_driver
+COMPONENT_DEPENDS := \
+	arch_driver \
+	SerialLib
 
 COMPONENT_VARS	+= USE_US_TIMER
 USE_US_TIMER	?= 1

Sming/Arch/Host/Components/driver/uart.rst

@@ -6,7 +6,8 @@ Host UART driver
 Introduction
 ------------
 
-Implements a UART driver to connect via TCP sockets, allowing terminal emulation using telnet.
+Implements a UART driver to connect via TCP socket, allowing terminal emulation using telnet,
+or directly to local host serial device (e.g. /dev/ttyUSB0, COM4, etc.)
 
 By default, output to UART0 is sent to the console and keyboard input is written to the UART0 receive queue.
 If emulation is enabled on any ports then this behaviour is disabled.
@@ -44,11 +45,9 @@ Build variables
 
    Allows full customisation of UART command-line options for ``make run``.
 
-   You should not need to change this for normal use.
 
-
-Usage
------
+TCP port emulation
+------------------
 
 Set required ports for emulation using the :envvar:`ENABLE_HOST_UARTID`, then execute ``make run``.
 
@@ -79,3 +78,26 @@ output at startup.)
 Port numbers are allocated sequentially from 10000. If you want to use
 different port numbers, set :envvar:`HOST_UART_PORTBASE`.
 
+
+Physical device connection
+--------------------------
+
+Override :envvar:`HOST_UART_OPTIONS` adding the `--device` option. For example::
+
+   make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0"
+
+The ``--device`` option must follow the ``--uart`` option. Another example::
+
+   make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0 --uart=1 --device=/dev/ttyUSB1"
+
+The port is opened when ``uart_init()`` gets called.
+
+The default baud rate is whatever the application has requested. This can be overridden as follows::
+
+   make run HOST_UART_OPTIONS="--uart=0 --device=/dev/ttyUSB0 --baud=921600"
+
+For Windows, substitute the appropriate device name, e.g. ``COM4`` instead of ``/dev/ttyUSB0``.
+
+.. note::
+
+   If necessary, add ``ENABLE_HOST_UARTID=`` to prevent telnet windows from being created.