• Masahiro Yamada's avatar
    kbuild: show hint if subdir-y/m is used to visit module Makefile · c07d8d47
    Masahiro Yamada authored
    Since commit ff9b45c5 ("kbuild: modpost: read modules.order instead
    of $(MODVERDIR)/*.mod"), a module is no longer built in the following
    pattern:
    
      [Makefile]
      subdir-y := some-module
    
      [some-module/Makefile]
      obj-m := some-module.o
    
    You cannot write Makefile this way in upstream because modules.order is
    not correctly generated. subdir-y is used to descend to a sub-directory
    that builds tools, device trees, etc.
    
    For external modules, the modules order does not matter. So, the
    Makefile above was known to work.
    
    I believe the Makefile should be re-written as follows:
    
      [Makefile]
      obj-m := some-module/
    
      [some-module/Makefile]
      obj-m := some-module.o
    
    However, people will have no idea if their Makefile suddenly stops
    working. In fact, I received questions from multiple people.
    
    Show a warning for a while if obj-m is specified in a Makefile visited
    by subdir-y or subdir-m.
    
    I touched the %/ rule to avoid false-positive warnings for the single
    target.
    
    Cc: Jan Kiszka <jan.kiszka@siemens.com>
    Cc: Tom Stonecypher <thomas.edwardx.stonecypher@intel.com>
    Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
    Tested-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
    c07d8d47
Makefile.build 17.3 KB