zephyr-kernel: Add 'zephyr' toolchain variant

Add an option to build applications using the Zephyr SDK by specifying
ZEPHYR_TOOLCHAIN_VARIANT="zephyr". This mode works with the zephyr or
poky distros (TCMODE is ignored), allowing Zephyr applications to be
built alongside a Linux stack.

Provide a toolchain-specific inc file for the Zephyr SDK, which
configures the dependencies and CMake appropriately.

Add Zephyr toolchain variant to CI configuration for qemu-cortex-a53,
qemu-cortex-m3 and qemu-x86. Update README.txt

Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Tested-by: Jon Mason <jon.mason@arm.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

.gitlab-ci.yml

@@ -79,6 +79,9 @@ nrf52840dk-nrf52840:
 
 qemu-cortex-a53:
   extends: .build
+  parallel:
+    matrix:
+      - TOOLCHAIN: [default, zephyr-toolchain]
 
 qemu-cortex-m0:
   extends: .build
@@ -90,7 +93,8 @@ qemu-cortex-m3:
   extends: .build
   parallel:
     matrix:
-      - TESTING: testimage
+      - TOOLCHAIN: [default, zephyr-toolchain]
+        TESTING: testimage
 
 qemu-cortex-r5:
   extends: .build
@@ -102,7 +106,8 @@ qemu-x86:
   extends: .build
   parallel:
     matrix:
-      - TESTING: testimage
+      - TOOLCHAIN: [default, zephyr-toolchain]
+        TESTING: testimage
 
 stm32mp157c-dk2:
   extends: .build

README.txt

@@ -14,9 +14,6 @@ This layer depends on:
     Python layer (meta-openembedded/meta-python)
         git://git.openembedded.org/meta-openembedded
 
-Modify local conf by adding:
-    DISTRO="zephyr"
-
 Add "meta-openembedded/meta-oe" to BBLAYERS
 Add "meta-openembedded/meta-python" to BBLAYERS
 Add "meta-zephyr-core" and "meta-zephyr-bsp" to BBLAYERS
@@ -25,6 +22,13 @@ Building and Running Zephyr Samples
 ===================================
 
 You can build Zephyr samples. There are several sample recipes.
+
+To use the Yocto toolchain, modify local conf by adding:
+    DISTRO="zephyr"
+
+To use the Zephyr pre-built toolchain, modify local conf by adding:
+    ZEPHYR_TOOLCHAIN_VARIANT = "zephyr"
+
 For example, to build the Zephyr "philosophers" sample:
     
     $ MACHINE=qemu-x86 bitbake zephyr-philosophers

ci/zephyr-toolchain.yml

@@ -0,0 +1,11 @@
+header:
+  version: 11
+
+# The Zephyr toolchain is standalone and does not depend on TCMODE or TCLIB, so
+# validate that it is possible to build Zephyr applications alongside a
+# poky-based Linux distro
+distro: poky
+
+local_conf_header:
+  zephyr-toolchain: |
+    ZEPHYR_TOOLCHAIN_VARIANT = "zephyr"

meta-zephyr-core/recipes-kernel/zephyr-kernel/zephyr-toolchain-zephyr.inc

@@ -0,0 +1,15 @@
+# Additional definitions to use the Zephyr SDK
+
+# Configure usage of the Zephyr SDK
+INHIBIT_DEFAULT_DEPS = "1"
+DEPENDS += "zephyr-sdk-native"
+export ZEPHYR_SDK_INSTALL_DIR="${STAGING_DIR_NATIVE}${prefix}/zephyr-sdk"
+OE_TERMINAL_EXPORTS += "ZEPHYR_SDK_INSTALL_DIR"
+
+# The Zephyr SDK does not require a CMake toolchain file
+EXTRA_OECMAKE:append = " -DCMAKE_TOOLCHAIN_FILE="
+deltask generate_toolchain_file
+
+# Provide a suitable location to store the toolchain capabilites cache
+ZEPHYR_USER_CACHE_DIR = "${B}/.cache"
+EXTRA_OECMAKE:append = " -DUSER_CACHE_DIR=${ZEPHYR_USER_CACHE_DIR}"