Support Esp8266 PHY settings runtime modification (#2830)

The initial PHY data is used initialize an ESP8266 chip and controls its behaviour.
This is stored in the ``phy_init`` partition and is loaded at startup.

Sometimes you may want to change that data for a certain ROM on the device without changing it for all ROMs on the device.

To do this, build with ``ENABLE_CUSTOM_PHY=1`` and add code to your application:

```
#include <esp_phy.h>

void customPhyInit(PhyInitData data)
{
   // Use methods of `data` to modify as required
 data.set_vdd33_const(0xff);
}
```

This PR supersedes #1491 and provides a more C++ mechanism for adjusting the configuration at runtime.

Sming/Arch/Esp8266/Components/esp8266/README.rst

@@ -8,3 +8,27 @@ support code.
 
 Sming uses libraries from the ESP8266 NON-OS SDK version 3, imported as a submodule.
 The header and linker files are provided by this Component.
+
+
+.. envvar:: ENABLE_CUSTOM_PHY
+
+   Default: undefined (off)
+
+   The ``phy_init`` partition contains data which the ESP8266 SDK uses to initialise WiFi hardware at startup.
+
+   You may want to change settings for a certain ROM on the device without changing it for all ROMs on the device.
+   To do this, build with ``ENABLE_CUSTOM_PHY=1`` and add code to your application::
+
+      #include <esp_phy.h>
+
+      void customPhyInit(PhyInitData data)
+      {
+         // Use methods of `data` to modify as required
+      	data.set_vdd33_const(0xff);
+      }
+
+   See :cpp:struct:`PhyInitData` for further details.
+
+
+.. doxygenstruct:: PhyInitData
+    :members:

Sming/Arch/Esp8266/Components/esp8266/component.mk

@@ -13,6 +13,15 @@ ifeq ($(DISABLE_WIFI),1)
 COMPONENT_DEPENDS	+= esp-lwip
 endif
 
+
+COMPONENT_RELINK_VARS += ENABLE_CUSTOM_PHY
+ENABLE_CUSTOM_PHY ?= 0
+ifeq ($(ENABLE_CUSTOM_PHY),1)
+	COMPONENT_CXXFLAGS += -DENABLE_CUSTOM_PHY=1
+	LDFLAGS += $(call Wrap,register_chipv6_phy)
+endif
+
+
 $(FLASH_INIT_DATA): $(SDK_BASE)/.submodule
 	$(Q) cp -f $(@D)/esp_init_data_default_v08.bin $@
 
@@ -29,7 +38,8 @@ export SDK_LIBDIR
 
 COMPONENT_DOXYGEN_INPUT := \
 	include/gpio.h \
-	include/pwm.h
+	include/pwm.h \
+	include/esp_phy.h
 
 # Crash handler hooks this so debugger can be invoked
 EXTRA_LDFLAGS := $(call Wrap,system_restart_local)

Sming/Arch/Esp8266/Components/esp8266/esp8266_phy.cpp

@@ -0,0 +1,43 @@
+/*
+ Adapted from Arduino for Sming.
+ Original copyright note is kept below.
+
+ phy.c - ESP8266 PHY initialization data
+ Copyright (c) 2015 Ivan Grokhotkov. All rights reserved.
+ This file is part of the esp8266 core for Arduino environment.
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+// #ifdef ENABLE_CUSTOM_PHY
+
+#include "include/esp_phy.h"
+#include <Storage.h>
+#include <esp_attr.h>
+#include <sys/pgmspace.h>
+#include <string.h>
+
+extern "C" {
+extern int __wrap_register_chipv6_phy(uint8_t* initData);
+extern int __real_register_chipv6_phy(uint8_t* initData);
+}
+
+int ICACHE_RAM_ATTR __wrap_register_chipv6_phy(uint8_t* initData)
+{
+	if(initData != NULL) {
+		PhyInitData data{initData};
+		customPhyInit(data);
+	}
+	return __real_register_chipv6_phy(initData);
+}
+
+// #endif /* ENABLE_CUSTOM_PHY */