From 1f66c0f3ee2696ed9a7bdae9c2b08759b1bfe42e Mon Sep 17 00:00:00 2001
From: Francisco Molina <femolina@uc.cl>
Date: Sat, 14 Dec 2019 23:16:01 +0100
Subject: [PATCH 1/4] Makefile.include: RIOTBOARD as BOARDSDIR fallback

---
 Makefile.include | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/Makefile.include b/Makefile.include
index 7b551e44d8..2e1f8b8cbe 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -158,6 +158,20 @@ else
 
 all: link
 
+# Include Board and CPU configuration, if BOARD is not found in BOARDSDIR
+# e.g. when set by the environment fallback to searching in RIOTBOARD
+ifeq (,$(wildcard $(BOARDSDIR)/$(BOARD)/.))
+  ifneq ($(RIOTBOARD),$(BOARDSDIR))
+    # The specified board $(BOARD) was not found in $(BOARDSDIR) fallback to RIOTBOARD
+    BOARDSDIR = $(RIOTBOARD)
+  endif
+  ifeq ($(RIOTBOARD),$(BOARDSDIR))
+    ifeq (,$(wildcard $(BOARDSDIR)/$(BOARD)/.))
+      $(error The specified board $(BOARD) does not exist.)
+    endif
+  endif
+endif
+
 include $(RIOTMAKE)/info.inc.mk
 
 # Static code analysis tools provided by LLVM
@@ -265,9 +279,6 @@ LAZYSPONGE_FLAGS ?= $(if $(filter 1,$(QUIET)),,--verbose)
 ifeq (, $(APPLICATION))
     $(error An application name must be specified as APPLICATION.)
 endif
-ifneq (0,$(shell test -d $(BOARDSDIR)/$(BOARD); echo $$?))
-    $(error The specified board $(BOARD) does not exist.)
-endif
 
 # Use TOOLCHAIN environment variable to select the toolchain to use.
 # Default for macOS: llvm; for other OS: gnu

From 18444ac99a461181cf24370c29b7956847b727e9 Mon Sep 17 00:00:00 2001
From: Francisco Molina <femolina@uc.cl>
Date: Sun, 15 Dec 2019 10:40:54 +0100
Subject: [PATCH 2/4] makefiles/boards.inc.mk: include BOARDSDIR and RIOTBOARD

---
 makefiles/boards.inc.mk | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/makefiles/boards.inc.mk b/makefiles/boards.inc.mk
index 7a56a238fc..27fe0b3836 100644
--- a/makefiles/boards.inc.mk
+++ b/makefiles/boards.inc.mk
@@ -1,10 +1,18 @@
 # Default when RIOTBASE is not set and is executed from the RIOT directory
 BOARDSDIR ?= $(or $(RIOTBASE),$(CURDIR))/boards
 
-# List all boards.
+# List all boards in a directory
 # By default, all directories in BOARDSDIR except 'common'
 #   use 'wildcard */.' to only list directories
-ALLBOARDS ?= $(sort $(filter-out common,$(patsubst $(BOARDSDIR)/%/.,%,$(wildcard $(BOARDSDIR)/*/.))))
+_get_boards_in_directory = $(filter-out common,$(patsubst $1/%/.,%,$(wildcard $1/*/.)))
+
+# If BOARDSDIR is not in RIOTBOARD also list BOARDS in RIOTBOARD
+ifneq ($(RIOTBOARD),$(BOARDSDIR))
+  ALLBOARDS_RIOTBOARD ?= $(call _get_boards_in_directory,$(RIOTBOARD))
+endif
+
+# Get all boards
+ALLBOARDS ?= $(sort $(call _get_boards_in_directory,$(BOARDSDIR)) $(ALLBOARDS_RIOTBOARD))
 
 # Set the default value from `BOARDS`
 BOARDS ?= $(ALLBOARDS)

From cacdd5634864a5510b2d9558db54ecb322a3c75e Mon Sep 17 00:00:00 2001
From: Francisco Molina <femolina@uc.cl>
Date: Sat, 14 Dec 2019 23:17:04 +0100
Subject: [PATCH 3/4] makefiles/info-global.inc.mk: RIOTBOAR as BOARDSDIR
 fallback

---
 makefiles/info-global.inc.mk | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/makefiles/info-global.inc.mk b/makefiles/info-global.inc.mk
index c51b2a1237..b99eda1096 100644
--- a/makefiles/info-global.inc.mk
+++ b/makefiles/info-global.inc.mk
@@ -1,6 +1,7 @@
 .PHONY: info-buildsizes info-buildsizes-diff info-features-missing \
         info-boards-features-missing
 
+BOARDSDIR_GLOBAL := $(BOARDSDIR)
 USEMODULE_GLOBAL := $(USEMODULE)
 USEPKG_GLOBAL := $(USEPKG)
 FEATURES_REQUIRED_GLOBAL := $(FEATURES_REQUIRED)
@@ -13,6 +14,7 @@ FEATURES_BLACKLIST_GLOBAL := $(FEATURES_BLACKLIST)
 
 define board_unsatisfied_features
   BOARD             := $(1)
+  BOARDSDIR         := $(BOARDSDIR_GLOBAL)
   USEMODULE         := $(USEMODULE_GLOBAL)
   USEPKG            := $(USEPKG_GLOBAL)
   DISABLE_MODULE    := $(DISABLE_MODULE_GLOBAL)
@@ -31,6 +33,12 @@ define board_unsatisfied_features
   undefine CPU
   undefine CPU_MODEL
 
+  # Replicate Makefile.include handling that sets BOARDSDIR to RIOTBOARD
+  # when BOARD is not found in BOARDSDIR
+  ifeq (,$(wildcard $(BOARDSDIR_GLOBAL)/$(BOARD)/.))
+    BOARDSDIR = $(RIOTBOARD)
+  endif
+
   include $(RIOTBASE)/Makefile.features
 
   include $(RIOTMAKE)/defaultmodules.inc.mk

From 33dbf9dfcde7db1f0a5d3cbfe768834469626431 Mon Sep 17 00:00:00 2001
From: Francisco Molina <femolina@uc.cl>
Date: Sun, 22 Dec 2019 09:48:42 +0100
Subject: [PATCH 4/4] tests/external_board_native: require arch_native

---
 tests/external_board_native/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/external_board_native/Makefile b/tests/external_board_native/Makefile
index 94c1ef91bf..a8dab58549 100644
--- a/tests/external_board_native/Makefile
+++ b/tests/external_board_native/Makefile
@@ -9,6 +9,10 @@ RIOTBASE ?= $(CURDIR)/../../
 # In practice it should be something else
 BOARD ?= native
 
+# Require arch_native feature so this is not compiled for other boards in
+# $(RIOTBOARD)/
+FEATURES_REQUIRED += arch_native
+
 # Set without '?=' to also verify the docker integration when set with =
 BOARDSDIR = $(CURDIR)/external_boards