BitBake Classes

What are BitBake Classes?

BitBake classes are files that typically contain functions and variables that are common in multiple recipes. These recipes then inherit the class in order to gain access to functions and variable. Thus, allowing multiple recipes a way acquire simaliar functionality without needing to implement the specific functionality on an individual bases.

In terms of writing a class it’s no different than writing a recipe. Just make sure your custom class is placed in your layers classes directory with the suffix .bbclass.

Normally Used Classes

• core-image.bbclass

  Used by most system image recipes (core-image-base.bb) to build the final system image.

• native.bbclass

  Typically inherited via BBCLASSEXTNED. Enables a recipe

  to be installed on the native (host) side of a recipes

  working environment RECIPE_SYSROOT_NATIVE.

  BBCLASSEXTEND += "native"
  

• nativesdk.bbclass

  Typically inherited via BBCLASSEXTNED. Enables a recipe

  to be installed on the native (host) side of the SDK.

  BBCLASSEXTEND += "nativesdk"
  

• pkgconfig.bbclass

  Useful to select what project configurations you want along with

  any given dependecies that particular configuration requires.

  Any configuration you want to request need to be added into the

  PACKAGECONFIG variable. The PACKAGECONFIG variable is

  formatted as such:

  PACKAGECONFIG[feature] = "Configuration if specified in PACKAGECONFIG, Configuration if not specified in PACKAGECONFIG, dependencies"
  

  Bellow shows typical use case with BitBake classes.

• meson.bbclass

  May be used to simplify building of meson based projects. Typical recipes that

  build projects with meson as build system have something like such.

  # Corresponds to meson options in kmsroots/meson_options.txt
  PACKAGECONFIG[examples] = "-Dexamples=true,-Dexamples=false,"
  PACKAGECONFIG[tests] = "-Dtests=true,-Dtests=false,"
  PACKAGECONFIG[debugging] = "-Ddebugging=enabled,-Ddebugging=disabled,"
  PACKAGECONFIG[kms] = "-Dkms=enabled,-Dkms=disabled,libdrm virtual/libgbm"
  PACKAGECONFIG[libseat] = "-Dlibseat=enabled,-Dlibseat=disabled,systemd udev seatd"
  PACKAGECONFIG[libinput] = "-Dlibinput=enabled,-Dlibinput=disabled,libinput"
  PACKAGECONFIG[xcb] = "-Dxcb=enabled,Dxcb=disabled,libxcb xcb-util-wm"
  PACKAGECONFIG[wayland] = "-Dwayland=enabled,-Dwayland=disabled,wayland wayland-native"
  PACKAGECONFIG[shaderc] = "-Dshaderc=enabled,-Dshaderc=disabled,shaderc glslang"
  
  PACKAGECONFIG ??= "kms xcb wayland libseat libinput shaderc"
  
  inherit meson pkgconfig
  
  EXTRA_OEMESON += "--buildtype release"
  

• cmake.bbclass

  May be used to simplify building of cmake based projects. Typical recipes that

  build projects with cmake as build system have something like such.

  PACKAGECONFIG[feature-openxr-service] = "-DXRT_FEATURE_SERVICE=ON,-DXRT_FEATURE_SERVICE=OFF,"
  PACKAGECONFIG[opengl] = "-DXRT_HAVE_OPENGL=ON,-DXRT_HAVE_OPENGL=OFF,virtual/libgl"
  PACKAGECONFIG[openglx] = "-DXRT_HAVE_OPENGL_GLX=ON,-DXRT_HAVE_OPENGL_GLX=OFF,virtual/libglx"
  PACKAGECONFIG[opengles] = "-DXRT_HAVE_OPENGLES=ON,-DXRT_HAVE_OPENGLES=OFF,virtual/libgles1 virtual/libgles2"
  PACKAGECONFIG[egl] = "-DXRT_HAVE_EGL=ON,-DXRT_HAVE_EGL=OFF,virtual/egl"
  #PACKAGECONFIG[realsense] = "-DXRT_HAVE_REALSENSE=ON,-DXRT_HAVE_REALSENSE=OFF,"
  PACKAGECONFIG[hidapi] = "-DXRT_HAVE_HIDAPI=ON,-DXRT_HAVE_HIDAPI=OFF,hidapi"
  PACKAGECONFIG[wayland] = "-DXRT_HAVE_WAYLAND=ON -DXRT_HAVE_WAYLAND_DIRECT=ON, \
                            -DXRT_HAVE_WAYLAND=OFF -DXRT_HAVE_WAYLAND_DIRECT=OFF, \
                            wayland-native wayland wayland-protocols libdrm"
  PACKAGECONFIG[sdl2] = "-DXRT_HAVE_SDL2=ON,-DXRT_HAVE_SDL2=OFF,libsdl2"
  
  PACKAGECONFIG ??= "\
      ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', 'feature-openxr-service', '', d)} \
      ${@bb.utils.contains('DISTRO_FEATURES', 'opengl', 'opengl opengles egl', '', d)} \
      ${@bb.utils.contains('DISTRO_FEATURES', 'opengl x11', 'openglx', '', d)} \
      ${@bb.utils.contains('DISTRO_FEATURES', 'wayland', 'wayland', '', d)} \
      "
  
  inherit cmake pkgconfig
  
  EXTRA_OECMAKE += "-DBUILD_SHARED_LIBS=ON"
  

• autotools.bbclass & autotools-brokensep.bbclass

  May be used to simplify building of autools based projects. Typical recipes that

  build projects with autotools as build system have something like such.

  PACKAGECONFIG[curses] = "--enable-curses,--disable-curses,ncurses"
  
  PACKAGECONFIG ??= "curses"
  
  inherit autools autotools-brokensep pkgconfig
  

• base.bbclass

  Not something you typically need to inherit directly.

  Contains implementation of oe_runmake.