Build: Move V4L2 detection into its own module

Improves detection across different platforms (esp. FreeBSD) since system paths are automatically taken into account (this is in contrast to check_include_file).

CMakeLists.txt

@@ -268,7 +268,6 @@ if(ZM_SYSTEMD OR (IS_DIRECTORY /usr/lib/systemd/system) OR (IS_DIRECTORY /lib/sy
 endif()
 
 # System checks
-check_include_file("linux/videodev2.h" HAVE_LINUX_VIDEODEV2_H)
 check_include_file("execinfo.h" HAVE_EXECINFO_H)
 if(HAVE_EXECINFO_H)
   check_function_exists("backtrace" HAVE_DECL_BACKTRACE)
@@ -530,15 +529,16 @@ endif()
 
 # Check for V4L header files and enable ZM_HAS_V4L, ZM_HAS_V4L2 accordingly
 # Setting to zeros first is required because ZM uses #define for these
+find_package(V4L2)
 set(ZM_HAS_V4L 0)
 set(ZM_HAS_V4L2 0)
-if(HAVE_LINUX_VIDEODEV2_H)
+if(TARGET V4L2::videodev2)
   set(ZM_HAS_V4L 1)
   set(ZM_HAS_V4L2 1)
-endif()
+else()
-if(NOT HAVE_LINUX_VIDEODEV2_H)
   message(AUTHOR_WARNING "Video 4 Linux headers weren't found - Analog and USB camera support will not be available")
 endif()
+
 # Check for PCRE and enable ZM_PCRE accordingly
 set(ZM_PCRE 0)
 if(HAVE_LIBPCRE AND HAVE_PCRE_H)

cmake/Modules/FindV4L2.cmake

@@ -0,0 +1,99 @@
+#[=======================================================================[.rst:
+FindV4L2
+----------
+
+Find V4L2 headers and libv4l2
+
+
+This module accepts optional COMPONENTS:
+
+  videodev2 (default)
+  libv4l2
+
+IMPORTED Targets
+^^^^^^^^^^^^^^^^
+
+This module defines the following :prop_tgt:`IMPORTED` targets::
+
+``V4L2::videodev2``
+  The Video for Linux Two header file, if found.
+``V4L2::libv4l2``
+  A thin abstraction layer on top of video4linux2 devices, if found.
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+``V4L2_FOUND``
+  System has v4l2 support. If no components are specified only the videodev2.h header has to be found.
+``V4L2_INCLUDE_DIRS``
+  The v4l2 include directories.
+``V4L2_LIBRARIES``
+  The libraries needed to have v4l2 support according to the specified components.
+#]=======================================================================]
+
+find_path(V4L2_VIDEODEV2_INCLUDE_DIR
+  NAMES linux/videodev2.h)
+mark_as_advanced(V4L2_VIDEODEV2_INCLUDE_DIR)
+
+if(EXISTS "${V4L2_VIDEODEV2_INCLUDE_DIR}")
+  set(V4L2_videodev2_FOUND TRUE)
+else()
+  set(V4L2_videodev2_FOUND FALSE)
+endif()
+
+pkg_check_modules(PC_V4L2_LIBV4L2 QUIET libv4l2)
+
+find_path(V4L2_LIBV4L2_INCLUDE_DIR
+  NAMES libv4l2.h
+  HINTS
+    ${PC_V4L2_LIBV4L2_INCLUDEDIR}
+    ${PC_V4L2_LIBV4L2_INCLUDE_DIRS})
+mark_as_advanced(V4L2_LIBV4L2_INCLUDE_DIR)
+
+find_library(V4L2_LIBV4L2_LIBRARY
+  NAMES ${PC_V4L2_LIBV4L2_LIBRARIES}
+  HINTS
+    ${PC_V4L2_LIBV4L2_LIBDIR}
+    ${PC_V4L2_LIBV4L2_LIBRARY_DIR})
+mark_as_advanced(V4L2_LIBV4L2_LIBRARY)
+
+if(EXISTS "${V4L2_LIBV4L2_INCLUDE_DIR}" AND
+  EXISTS "${V4L2_LIBV4L2_LIBRARY}")
+  set(V4L2_libv4l2_FOUND TRUE)
+else()
+  set(V4L2_libv4l2_FOUND FALSE)
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(V4L2
+  REQUIRED_VARS
+    V4L2_VIDEODEV2_INCLUDE_DIR
+  HANDLE_COMPONENTS)
+
+set(V4L2_INCLUDE_DIRS)
+set(V4L2_LIBRARIES)
+
+if(V4L2_videodev2_FOUND)
+  set(V4L2_VIDEODEV2_INCLUDE_DIRS ${V4L2_VIDEODEV2_INCLUDE_DIR})
+  list(APPEND V4L2_INCLUDE2_DIRS
+    "${V4L2_VIDEODEV2_INCLUDE_DIRS}")
+
+  add_library(V4L2::videodev2 INTERFACE IMPORTED)
+  set_target_properties(V4L2::videodev2 PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${V4L2_VIDEODEV2_INCLUDE_DIRS}")
+endif()
+
+if(V4L2_libv4l2_FOUND)
+  set(V4L2_LIBV4L2_INCLUDE_DIRS ${V4L2_LIBV4L2_INCLUDE_DIR})
+  set(V4L2_LIBV4L2_LIBRARIES ${V4L2_LIBV4L2_LIBRARY})
+
+  list(APPEND V4L2_INCLUDE_DIRS
+    "${V4L2_LIBV4L2_INCLUDE_DIRS}")
+  list(APPEND V4L2_LIBRARIES
+    "${V4L2_LIBV4L2_LIBRARIES}")
+
+  add_library(V4L2::libv4l2 UNKNOWN IMPORTED)
+  set_target_properties(V4L2::libv4l2 PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${V4L2_LIBV4L2_INCLUDE_DIRS}"
+    IMPORTED_LOCATION "${V4L2_LIBV4L2_LIBRARY}")
+endif()

src/CMakeLists.txt

@@ -98,6 +98,12 @@ elseif(${ZM_JWT_BACKEND} STREQUAL "libjwt")
       JWT::libjwt)
 endif()
 
+if(TARGET V4L2::videodev2)
+  target_link_libraries(zm
+    PRIVATE
+      V4L2::videodev2)
+endif()
+
 add_executable(zmc zmc.cpp)
 add_executable(zms zms.cpp)
 add_executable(zmu zmu.cpp)