################################################################################
  # kernel module infrastructure for building Linux kernel modules
  #
  # This file implements an infrastructure that eases development of package
  # .mk files for out-of-tree Linux kernel modules. It should be used for all
  # packages that build a Linux kernel module using the kernel's out-of-tree
  # buildsystem, unless they use a complex custom buildsystem.
  #
  # The kernel-module infrastructure requires the packages that use it to also
  # use another package infrastructure. kernel-module only defines post-build
  # and post-install hooks. This allows the package to build both kernel
  # modules and/or user-space components (with any of the other *-package
  # infra).
  #
  # As such, it is to be used in conjunction with another *-package infra,
  # like so:
  #
  #   $(eval $(kernel-module))
  #   $(eval $(generic-package))
  #
  # Note: if the caller needs access to the kernel modules (either after they
  # are built or after they are installed), it will have to define its own
  # post-build/install hooks *after* calling kernel-module, but *before*
  # calling the other *-package infra, like so:
  #
  #   $(eval $(kernel-module))
  #   define FOO_MOD_TWEAK
  #   	# do something
  #   endef
  #   FOO_POST_BUILD_HOOKS += FOO_MOD_TWEAK
  #   $(eval $(generic-package))
  #
  # Note: this infra does not check that the kernel is enabled; it is expected
  # to be enforced at the Kconfig level with proper 'depends on'.
  ################################################################################
  
  ################################################################################
  # inner-kernel-module -- generates the make targets needed to support building
  # a kernel module
  #
  #  argument 1 is the lowercase package name
  #  argument 2 is the uppercase package name
  ################################################################################
  
  define inner-kernel-module
  
  # If the package is enabled, ensure the kernel will support modules
  ifeq ($$(BR2_PACKAGE_$(2)),y)
  LINUX_NEEDS_MODULES = y
  endif
  
  # The kernel must be built first.
  $(2)_DEPENDENCIES += linux
  
  # This is only defined in some infrastructures (e.g. autotools, cmake),
  # but not in others (e.g. generic). So define it here as well.
  $(2)_MAKE ?= $$(MAKE)
  
  # If not specified, consider the source of the kernel module to be at
  # the root of the package.
  $(2)_MODULE_SUBDIRS ?= .
  
  # Build the kernel module(s)
  # Force PWD for those packages that want to use it to find their
  # includes and other support files (Booo!)
  define $(2)_KERNEL_MODULES_BUILD
  	@$$(call MESSAGE,"Building kernel module(s)")
  	$$(foreach d,$$($(2)_MODULE_SUBDIRS), \
  		$$(LINUX_MAKE_ENV) $$($$(PKG)_MAKE) \
  			-C $$(LINUX_DIR) \
  			$$(LINUX_MAKE_FLAGS) \
  			$$($(2)_MODULE_MAKE_OPTS) \
  			PWD=$$(@D)/$$(d) \
  			M=$$(@D)/$$(d) \
  			modules$$(sep))
  endef
  $(2)_POST_BUILD_HOOKS += $(2)_KERNEL_MODULES_BUILD
  
  # Install the kernel module(s)
  # Force PWD for those packages that want to use it to find their
  # includes and other support files (Booo!)
  define $(2)_KERNEL_MODULES_INSTALL
  	@$$(call MESSAGE,"Installing kernel module(s)")
  	$$(foreach d,$$($(2)_MODULE_SUBDIRS), \
  		$$(LINUX_MAKE_ENV) $$($$(PKG)_MAKE) \
  			-C $$(LINUX_DIR) \
  			$$(LINUX_MAKE_FLAGS) \
  			$$($(2)_MODULE_MAKE_OPTS) \
  			PWD=$$(@D)/$$(d) \
  			M=$$(@D)/$$(d) \
  			modules_install$$(sep))
  endef
  $(2)_POST_INSTALL_TARGET_HOOKS += $(2)_KERNEL_MODULES_INSTALL
  
  endef
  
  ################################################################################
  # kernel-module -- the target generator macro for kernel module packages
  ################################################################################
  
  kernel-module = $(call inner-kernel-module,$(pkgname),$(call UPPERCASE,$(pkgname)))