zephyr: add base files for Zephyr module

This adds the minimum files necessary for platform/ec to be considered
a Zephyr module, as well as some of the discussed CMakeLists files
from go/zephyr-shim.

BUG=b:167590251
BRANCH=none
TEST=Append platform/ec dir to ZEPHYR_MODULES, build for posix-ec

    To replicate:
    $ export ZEPHYR_TOOLCHAIN_VARIANT=llvm
    $ export ZEPHYR_BASE=...
    $ ZEPHYR_CHROME=...
    $ PLATFORM_EC=...
    $ cmake -S ${ZEPHYR_CHROME}/projects/experimental/posix-ec \
            -B /tmp/zephyr-build \
            -D ZEPHYR_MODULES="${ZEPHYR_CHROME};${PLATFORM_EC}"
    $ ninja -C /tmp/zephyr-build
    $ /tmp/zephyr-build/zephyr/zephyr.elf

Signed-off-by: Jack Rosenthal <jrosenth@chromium.org>
Change-Id: Id5eb4e4d3b761a9499e876dfe2178be7f7961e93
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2427089
Reviewed-by: Jett Rink <jettrink@chromium.org>

4 files changed, 56 insertions, 0 deletions

diff --git a/zephyr/CMakeLists.txt b/zephyr/CMakeLists.txt
new file mode 100644
index 0000000000..5c0866bd74
--- /dev/null
+++ b/zephyr/CMakeLists.txt
@@ -0,0 +1,27 @@
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Note: this cmake system implements only a zephyr module, and is not
+# intended to build a complete EC.  To build projects in platform/ec,
+# you should continue to use the Makefile system.
+#
+# Googlers can find the design doc at go/zephyr-shim.
+
+if(NOT DEFINED ZEPHYR_CURRENT_MODULE_DIR)
+  message(FATAL_ERROR "This Cmake system implements only a Zephyr module, and
+          should not be invoked directly.  Please continue to use the Makefile
+          system for non-Zephyr builds.")
+endif()
+
+set(PLATFORM_EC "${ZEPHYR_CURRENT_MODULE_DIR}/.." CACHE PATH
+    "Path to the platform/ec repo.")
+
+zephyr_include_directories_ifdef(
+  CONFIG_PLATFORM_EC
+  "${PLATFORM_EC}/zephyr/shim/include"
+  "${PLATFORM_EC}/fuzz"
+  "${PLATFORM_EC}/test"
+  "${PLATFORM_EC}/include")
+
+add_subdirectory_ifdef(CONFIG_PLATFORM_EC "shim/src")
diff --git a/zephyr/Kconfig b/zephyr/Kconfig
new file mode 100644
index 0000000000..be011de867
--- /dev/null
+++ b/zephyr/Kconfig
@@ -0,0 +1,17 @@
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+menuconfig PLATFORM_EC
+	bool "Enable building code from the platform/ec Zephyr module"
+	imply PRINTK
+	imply SHELL
+	help
+	  The platform/ec Zephyr module allows some code from the
+	  existing Chrome OS EC project to be "shimmed" into Zephyr.
+
+if PLATFORM_EC
+
+# Nothing here yet.
+
+endif # PLATFORM_EC
diff --git a/zephyr/module.yml b/zephyr/module.yml
new file mode 100644
index 0000000000..a8ea98bece
--- /dev/null
+++ b/zephyr/module.yml
@@ -0,0 +1,7 @@
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+build:
+  cmake: zephyr/
+  kconfig: zephyr/Kconfig
diff --git a/zephyr/shim/src/CMakeLists.txt b/zephyr/shim/src/CMakeLists.txt
new file mode 100644
index 0000000000..d3db874f71
--- /dev/null
+++ b/zephyr/shim/src/CMakeLists.txt
@@ -0,0 +1,5 @@
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Nothing here yet.