Issue 590 - Determine any libgpiod version and add to compile command line.

Author: wb2osz

CMakeLists.txt

@@ -324,6 +324,30 @@ endif()
 find_package(gpiod)
 if(GPIOD_FOUND)
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DUSE_GPIOD")
+
+  # Version 2 uses a completely different API.
+  # Try to determine version and put it on compile command line.
+
+  # Require pkg-config support
+  find_package(PkgConfig REQUIRED)
+  # Probe for libgpiod
+  pkg_check_modules(LIBGPIOD REQUIRED libgpiod)
+  # Abort if not found
+  if(NOT LIBGPIOD_FOUND)
+    message(FATAL_ERROR "libgpiod not found via pkg-config")
+  endif()
+
+  # LIBGPIOD_VERSION holds the full x.y.z string
+
+  # Now split out major and minor versions into separate integers
+  string(REPLACE "." ";" VLIST ${LIBGPIOD_VERSION})
+  list(GET VLIST 0 LIBGPIOD_VERSION_MAJOR)
+  list(GET VLIST 1 LIBGPIOD_VERSION_MINOR)
+  message(STATUS "libgpiod version ${LIBGPIOD_VERSION} major=${LIBGPIOD_VERSION_MAJOR} minor=${LIBGPIOD_VERSION_MINOR}")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DLIBGPIOD_VERSION=${LIBGPIOD_VERSION}")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DLIBGPIOD_VERSION_MAJOR=${LIBGPIOD_VERSION_MAJOR}")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DLIBGPIOD_VERSION_MINOR=${LIBGPIOD_VERSION_MINOR}")
+
 else()
   set(GPIOD_INCLUDE_DIRS "")
   set(GPIOD_LIBRARIES "")