[cmake] enable user specified mbedtls target (#4812)

This commit allows users to specify the mbedtls target by a
OT_EXTERNAL_MBEDTLS option.

The native cmake build system of mbedtls is not so "modern" (for
backward compatibility, it maybe hard to change it soon) and
applications using mbedtls are likely to write wrapper cmake files and
targets by themselves.

CMakeLists.txt

@@ -30,8 +30,8 @@ cmake_minimum_required(VERSION 3.13.1)
 project(openthread)
 
 option(OT_BUILD_EXECUTABLES "Build executables" ON)
-option(OT_BUILTIN_MBEDTLS "Enable builtin mbedTLS" ON)
 option(OT_COVERAGE "enable coverage" OFF)
+set(OT_EXTERNAL_MBEDTLS "" CACHE STRING "Specify external mbedtls library")
 
 include(TestBigEndian)
 TEST_BIG_ENDIAN(OT_BIG_ENDIAN)

etc/cmake/options.cmake

@@ -41,9 +41,11 @@ if(OT_BORDER_ROUTER)
     list(APPEND OT_PRIVATE_DEFINES "OPENTHREAD_CONFIG_BORDER_ROUTER_ENABLE=1")
 endif()
 
-if(OT_BUILTIN_MBEDTLS)
+if(NOT OT_EXTERNAL_MBEDTLS)
+    set(OT_MBEDTLS mbedtls)
     list(APPEND OT_PRIVATE_DEFINES "OPENTHREAD_CONFIG_ENABLE_BUILTIN_MBEDTLS=1")
 else()
+    set(OT_MBEDTLS ${OT_EXTERNAL_MBEDTLS})
     list(APPEND OT_PRIVATE_DEFINES "OPENTHREAD_CONFIG_ENABLE_BUILTIN_MBEDTLS=0")
 endif()
 

examples/platforms/cc1352/CMakeLists.txt

@@ -70,7 +70,7 @@ set_property(TARGET openthread-cc1352 PROPERTY C_STANDARD 99)
 target_link_libraries(openthread-cc1352
     PRIVATE
         "${PROJECT_SOURCE_DIR}/third_party/ti/devices/cc13x2_cc26x2/driverlib/bin/gcc/driverlib.a"
-        mbedtls
+        ${OT_MBEDTLS}
 )
 target_link_options(openthread-cc1352
     PUBLIC

examples/platforms/cc2650/CMakeLists.txt

@@ -71,7 +71,7 @@ target_link_libraries(openthread-cc2650
     PUBLIC
         cc26x0-driver
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
         openthread-platform-utils
 )
 

examples/platforms/cc2652/CMakeLists.txt

@@ -70,7 +70,7 @@ set_property(TARGET openthread-cc2652 PROPERTY C_STANDARD 99)
 target_link_libraries(openthread-cc2652
     PRIVATE
         "${PROJECT_SOURCE_DIR}/third_party/ti/devices/cc13x2_cc26x2/driverlib/bin/gcc/driverlib.a"
-        mbedtls
+        ${OT_MBEDTLS}
 )
 target_link_options(openthread-cc2652
     PUBLIC

examples/platforms/qpg6095/CMakeLists.txt

@@ -72,7 +72,7 @@ set_property(TARGET openthread-qpg6095 PROPERTY C_STANDARD 99)
 target_link_libraries(openthread-qpg6095
     PRIVATE
         qpg6095-driver
-        mbedtls
+        ${OT_MBEDTLS}
 )
 
 target_link_options(openthread-qpg6095

examples/platforms/samr21/CMakeLists.txt

@@ -70,7 +70,7 @@ target_link_libraries(openthread-samr21
     PUBLIC
         samr21-driver
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
 )
 
 target_link_options(openthread-samr21

src/cli/CMakeLists.txt

@@ -83,12 +83,12 @@ target_link_libraries(openthread-cli-ftd
     PUBLIC
         openthread-ftd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
 )
 
 target_link_libraries(openthread-cli-mtd
     PUBLIC
         openthread-mtd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
 )

src/core/CMakeLists.txt

@@ -245,10 +245,10 @@ target_sources(openthread-radio PRIVATE
 
 target_link_libraries(openthread-ftd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
 )
 
 target_link_libraries(openthread-mtd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
 )

src/ncp/CMakeLists.txt

@@ -105,7 +105,7 @@ target_link_libraries(openthread-ncp-ftd
     PUBLIC
         openthread-ftd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
         openthread-hdlc
         openthread-spinel-ncp
 )
@@ -114,7 +114,7 @@ target_link_libraries(openthread-ncp-mtd
     PUBLIC
         openthread-mtd
     PRIVATE
-        mbedtls
+        ${OT_MBEDTLS}
         openthread-hdlc
         openthread-spinel-ncp
 )

tests/unit/CMakeLists.txt

@@ -34,7 +34,7 @@ set(COMMON_SOURCES
 set(COMMON_LIBS
     openthread-ftd
     openthread-ncp-ftd
-    mbedtls
+    ${OT_MBEDTLS}
     util
 )
 

third_party/CMakeLists.txt

@@ -26,9 +26,10 @@
 #  POSSIBILITY OF SUCH DAMAGE.
 #
 
-if(OT_BUILTIN_MBEDTLS)
+if(NOT OT_EXTERNAL_MBEDTLS)
     add_subdirectory(mbedtls)
 endif()
+
 if(OT_PLATFORM STREQUAL "kw41z")
     add_subdirectory(nxp)
 elseif(OT_PLATFORM STREQUAL "cc2650")