#
#Yocto - Build-system for the Linux kernel
#
#Yocto runs on Linux only, because it depends on a plethora of command line
#utilities and Python version 2.7. Another fine mess created by the UNIX
#"toolkit" philosophy, complete with a bag of seeds to organically grow a
#"build machine" which eventually nobody knows the specs for. We must pretend
#to subscribe to the idea of the build machine in order to take advantage of
#Yocto to build a customized Linux kernel. This file completely automates
#setting up a Yocto build environment, thereby ensuring that the Yocto
#environment is set up in exactly the same way every time.
#
#NOTE NOTE NOTE
#There are no BUILD_COMMANDs defined here. The modules defined here will
#simply install everything we need in order to run bitbake with a number of
#Bitbake layers. We must invoke bitbake manually. Bitbake may then in turn
#invoke cmake in order to build any user level code we have defined in any
#.bb layers we may have introduced. That user level code will be included in
#the bootable SD card image generated by bitbake.
#

#The Yocto system and all layers go under UNPACKED_ROOT
set (UNPACKED_ROOT "${CMAKE_INSTALL_PREFIX}/yocto")

ExternalProject_Add (
  yocto
  PREFIX ${CMAKE_INSTALL_PREFIX}
  SOURCE_DIR ${UNPACKED_ROOT}/poky
  BUILD_IN_SOURCE 1
  URL http://downloads.yoctoproject.org/releases/yocto/yocto-3.1.12/poky-dunfell-23.0.12.tar.bz2
  URL_MD5 92cc07d8b0b85456dd9f523f5c366433
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
)

ExternalProject_Add (
  yocto-openembedded
  PREFIX ${CMAKE_INSTALL_PREFIX}
  SOURCE_DIR ${UNPACKED_ROOT}/meta-openembedded
  BUILD_IN_SOURCE 1
  URL http://downloads.yoctoproject.org/releases/yocto/yocto-3.1.12/meta-openembedded-dunfell-23.0.12.tar.bz2
  URL_MD5 2d368ec91815140eaa0a30f04dfe4a55
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
  DEPENDS yocto
)

#Yocto Board Support Package (BSP) for Linux on Raspberry Pi
ExternalProject_Add (
  yocto-raspberrypi
  PREFIX ${CMAKE_INSTALL_PREFIX}
  SOURCE_DIR ${UNPACKED_ROOT}/meta-raspberrypi
  BUILD_IN_SOURCE 1
# URL https://github.com/agherzan/meta-raspberrypi/archive/dunfell.zip
# Head of the Dunfell branch per 14dec21 is
  URL https://github.com/agherzan/meta-raspberrypi/archive/934064a01903b2ba9a82be93b3f0efdb4543a0e8.zip
  URL_MD5 fc0487669bf98ac028333334e6f9de19
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
  DEPENDS yocto-openembedded
)

ExternalProject_Add (
  yocto-hifiberry-rpi
  PREFIX ${CMAKE_INSTALL_PREFIX}
  SOURCE_DIR ${UNPACKED_ROOT}/meta-hifiberry-rpi
  BUILD_IN_SOURCE 1
# Head of the master branch per 28dec21 is
  URL https://github.com/mickey-happygolucky/meta-hifiberry-rpi/archive/5f71b99431e3b18db06040fd712618d871e3ebf9.zip
  URL_MD5 ed4b90c6e8b16da0118a30197f64947e
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
  DEPENDS yocto-openembedded
)

#Command to invoke "bitbake". Sets all required environment variables first.
#For example: "${BITBAKE_CMD} core-image-minimal -c populate_sdk_ext"
set (BITBAKE_CMD "${CMAKE_COMMAND} chdir ${UNPACKED_ROOT}/poky source ./oe-init-build-env && bitbake" PARENT_SCOPE)

#For use by other OSD modules that need to install their own Yocto layers.
#Yocto layer "A" must be installed under "${YOCTO_ROOT}/A". 
set (YOCTO_ROOT "${UNPACKED_ROOT}" PARENT_SCOPE)