# SPDX-License-Identifier: GPL-2.0

  # ==========================================================================
  # Installing headers
  #

  # All headers under include/uapi, include/generated/uapi,

  # arch/<arch>/include/uapi and arch/<arch>/include/generated/uapi are

  # exported.
  # They are preprocessed to remove __KERNEL__ section of the file.

  #
  # ==========================================================================

  PHONY := __headers
  __headers:
  
  include scripts/Kbuild.include

  src := $(srctree)/$(obj)
  gen := $(objtree)/$(subst include/,include/generated/,$(obj))
  dst := usr/include

  -include $(src)/Kbuild

  # $(filter %/, ...) is a workaround for GNU Make <= 4.2.1, where
  # $(wildcard $(src)/*/) contains not only directories but also regular files.
  src-subdirs := $(patsubst $(src)/%/,%,$(filter %/, $(wildcard $(src)/*/)))
  gen-subdirs := $(patsubst $(gen)/%/,%,$(filter %/, $(wildcard $(gen)/*/)))

  all-subdirs := $(sort $(src-subdirs) $(gen-subdirs))

  src-headers := $(if $(src-subdirs), $(shell cd $(src) && find $(src-subdirs) -name '*.h'))
  src-headers := $(filter-out $(no-export-headers), $(src-headers))
  gen-headers := $(if $(gen-subdirs), $(shell cd $(gen) && find $(gen-subdirs) -name '*.h'))
  gen-headers := $(filter-out $(no-export-headers), $(gen-headers))

  # If the same header is exported from source and generated directories,
  # the former takes precedence, but this should be warned.
  duplicated := $(filter $(gen-headers), $(src-headers))
  $(if $(duplicated), $(warning duplicated header export: $(duplicated)))

  gen-headers := $(filter-out $(duplicated), $(gen-headers))

  # Add dst path prefix
  all-subdirs := $(addprefix $(dst)/, $(all-subdirs))
  src-headers := $(addprefix $(dst)/, $(src-headers))
  gen-headers := $(addprefix $(dst)/, $(gen-headers))
  all-headers := $(src-headers) $(gen-headers)

  # Work out what needs to be removed
  old-subdirs := $(wildcard $(all-subdirs))
  old-headers := $(if $(old-subdirs),$(shell find $(old-subdirs) -name '*.h'))
  unwanted    := $(filter-out $(all-headers), $(old-headers))

  # Create directories
  existing-dirs := $(sort $(dir $(old-headers)))
  wanted-dirs   := $(sort $(dir $(all-headers)))
  new-dirs      := $(filter-out $(existing-dirs), $(wanted-dirs))
  $(if $(new-dirs), $(shell mkdir -p $(new-dirs)))

  # Rules

  quiet_cmd_install = HDRINST $@

        cmd_install = $(CONFIG_SHELL) $(srctree)/scripts/headers_install.sh $< $@

  $(src-headers): $(dst)/%.h: $(src)/%.h $(srctree)/scripts/headers_install.sh FORCE
  	$(call if_changed,install)

  $(gen-headers): $(dst)/%.h: $(gen)/%.h $(srctree)/scripts/headers_install.sh FORCE
  	$(call if_changed,install)

  quiet_cmd_remove = REMOVE  $(unwanted)

        cmd_remove = rm -f $(unwanted)

  __headers: $(all-headers)
  ifneq ($(unwanted),)
  	$(call cmd,remove)
  endif

  	@:

  existing-headers := $(filter $(old-headers), $(all-headers))
  
  -include $(foreach f,$(existing-headers),$(dir $(f)).$(notdir $(f)).cmd)

  PHONY += FORCE

  FORCE:

  
  .PHONY: $(PHONY)