esp8266: Rework board variant support to require mpconfigvariant file.

Following how esp32 has been reworked, each variant now has a corresponding
`mpconfigvariant_VARIANT.mk` file associated with it.  The base variant
also has a `mpconfigvariant.mk` file because it has options that none of
the other variants use.

Signed-off-by: Damien George <damien@micropython.org>

ports/esp8266/Makefile

@@ -16,6 +16,12 @@ endif
 $(error Invalid BOARD specified: $(BOARD_DIR))
 endif
 
+ifneq ($(BOARD_VARIANT),)
+ifeq ($(wildcard $(BOARD_DIR)/mpconfigvariant_$(BOARD_VARIANT).mk),)
+$(error Invalid BOARD_VARIANT specified: $(BOARD_VARIANT))
+endif
+endif
+
 # If the build directory is not given, make it reflect the board name (and
 # optionally the board variant).
 ifneq ($(BOARD_VARIANT),)
@@ -26,8 +32,13 @@ endif
 
 include ../../py/mkenv.mk
 
-# Optional
--include $(BOARD_DIR)/mpconfigboard.mk
+# Include board specific .mk file, and optional board variant .mk file.
+include $(BOARD_DIR)/mpconfigboard.mk
+ifeq ($(BOARD_VARIANT),)
+-include $(BOARD_DIR)/mpconfigvariant.mk
+else
+include $(BOARD_DIR)/mpconfigvariant_$(BOARD_VARIANT).mk
+endif
 
 # qstr definitions (must come before including py.mk)
 QSTR_DEFS = qstrdefsport.h #$(BUILD)/pins_qstr.h

ports/esp8266/boards/ESP8266_GENERIC/mpconfigboard.mk

@@ -1,50 +1 @@
-ifeq ($(BOARD_VARIANT),)
-LD_FILES = boards/esp8266_2MiB.ld
-
-MICROPY_PY_ESPNOW ?= 1
-MICROPY_PY_BTREE ?= 1
-MICROPY_VFS_FAT ?= 1
-MICROPY_VFS_LFS2 ?= 1
-
-# Add asyncio and extra micropython-lib packages (in addition to the port manifest).
-FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest_2MiB.py
-
-# Configure mpconfigboard.h.
-CFLAGS += -DMICROPY_ESP8266_2M
-endif
-
-ifeq ($(BOARD_VARIANT),FLASH_1M)
-LD_FILES = boards/esp8266_1MiB.ld
-
-MICROPY_PY_ESPNOW ?= 1
-MICROPY_PY_BTREE ?= 1
-MICROPY_VFS_LFS2 ?= 1
-
-# Note: Implicitly uses the port manifest.
-
-# Configure mpconfigboard.h.
-CFLAGS += -DMICROPY_ESP8266_1M
-endif
-
-ifeq ($(BOARD_VARIANT),OTA)
-LD_FILES = boards/esp8266_ota.ld
-
-MICROPY_PY_ESPNOW ?= 1
-MICROPY_PY_BTREE ?= 1
-MICROPY_VFS_LFS2 ?= 1
-
-# Note: Implicitly uses the port manifest.
-
-# Configure mpconfigboard.h.
-CFLAGS += -DMICROPY_ESP8266_1M
-endif
-
-ifeq ($(BOARD_VARIANT),FLASH_512K)
-LD_FILES = boards/esp8266_512kiB.ld
-
-# Note: Use the minimal manifest.py.
-FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest_512kiB.py
-
-# Configure mpconfigboard.h.
-CFLAGS += -DMICROPY_ESP8266_512K
-endif
+# There are no common .mk settings among the variants, so this file is empty.

ports/esp8266/boards/ESP8266_GENERIC/mpconfigvariant.mk

@@ -0,0 +1,12 @@
+LD_FILES = boards/esp8266_2MiB.ld
+
+MICROPY_PY_ESPNOW ?= 1
+MICROPY_PY_BTREE ?= 1
+MICROPY_VFS_FAT ?= 1
+MICROPY_VFS_LFS2 ?= 1
+
+# Add asyncio and extra micropython-lib packages (in addition to the port manifest).
+FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest_2MiB.py
+
+# Configure mpconfigboard.h.
+CFLAGS += -DMICROPY_ESP8266_2M

ports/esp8266/boards/ESP8266_GENERIC/mpconfigvariant_FLASH_1M.mk

@@ -0,0 +1,10 @@
+LD_FILES = boards/esp8266_1MiB.ld
+
+MICROPY_PY_ESPNOW ?= 1
+MICROPY_PY_BTREE ?= 1
+MICROPY_VFS_LFS2 ?= 1
+
+# Note: Implicitly uses the port manifest.
+
+# Configure mpconfigboard.h.
+CFLAGS += -DMICROPY_ESP8266_1M

ports/esp8266/boards/ESP8266_GENERIC/mpconfigvariant_FLASH_512K.mk

@@ -0,0 +1,7 @@
+LD_FILES = boards/esp8266_512kiB.ld
+
+# Note: Use the minimal manifest.py.
+FROZEN_MANIFEST ?= $(BOARD_DIR)/manifest_512kiB.py
+
+# Configure mpconfigboard.h.
+CFLAGS += -DMICROPY_ESP8266_512K

ports/esp8266/boards/ESP8266_GENERIC/mpconfigvariant_OTA.mk

@@ -0,0 +1,10 @@
+LD_FILES = boards/esp8266_ota.ld
+
+MICROPY_PY_ESPNOW ?= 1
+MICROPY_PY_BTREE ?= 1
+MICROPY_VFS_LFS2 ?= 1
+
+# Note: Implicitly uses the port manifest.
+
+# Configure mpconfigboard.h.
+CFLAGS += -DMICROPY_ESP8266_1M