• Masahiro Yamada's avatar
    kconfig: switch to single .config configuration · e02ee254
    Masahiro Yamada authored
    When Kconfig for U-boot was examined, one of the biggest issues was
    how to support multiple images (Normal, SPL, TPL).  There were
    actually two options, "single .config" and "multiple .config".
    After some discussions and thought experiments, I chose the latter,
    i.e. to create ".config", "spl/.config", "tpl/.config" for Normal,
    SPL, TPL, respectively.
    
    It is true that the "multiple .config" strategy provided us the
    maximum flexibility and helped to avoid duplicating CONFIGs among
    Normal, SPL, TPL, but I have noticed some fatal problems:
    
    [1] It is impossible to share CONFIG options across the images.
      If you change the configuration of Main image, you often have to
      adjust some SPL configurations correspondingly.  Currently, we
      cannot handle the dependencies between them.  It means one of the
      biggest advantages of Kconfig is lost.
    
    [2] It is too painful to change both ".config" and "spl/.config".
      Sunxi guys started to work around this problem by creating a new
      configuration target.  Commit cbdd9a97 (sunxi: kconfig: Add
      %_felconfig rule to enable FEL build of sunxi platforms.) added
      "make *_felconfig" to enable CONFIG_SPL_FEL on both images.
      Changing the configuration of multiple images in one command is a
      generic demand.  The current implementation cannot propose any
      good solution about this.
    
    [3] Kconfig files are getting ugly and difficult to understand.
      Commit b724bd7d (dm: Kconfig: Move CONFIG_SYS_MALLOC_F_LEN to
      Kconfig) has sprinkled "if !SPL_BUILD" over the Kconfig files.
    
    [4] The build system got more complicated than it should be.
      To adjust Linux-originated Kconfig to U-Boot, the helper script
      "scripts/multiconfig.sh" was introduced.  Writing a complicated
      text processor is a shell script sometimes caused problems.
    
    Now I believe the "single .config" will serve us better.  With it,
    all the problems above would go away.  Instead, we will have to add
    some CONFIG_SPL_* (and CONFIG_TPL_*) options such as CONFIG_SPL_DM,
    but we will not have much.  Anyway, this is what we do now in
    scripts/Makefile.spl.
    
    I admit my mistake with my apology and this commit switches to the
    single .config configuration.
    
    It is not so difficult to do that:
    
     - Remove unnecessary processings from scripts/multiconfig.sh
      This file will remain for a while to support the current defconfig
      format.  It will be removed after more cleanups are done.
    
     - Adjust some makefiles and Kconfigs
    
     - Add some entries to include/config_uncmd_spl.h and the new file
       scripts/Makefile.uncmd_spl.  Some CONFIG options that are not
       supported on SPL must be disabled because one .config is shared
       between SPL and U-Boot proper going forward.  I know this is not
       a beautiful solution and I think we can do better, but let's see
       how much we will have to describe them.
    
     - update doc/README.kconfig
    
    More cleaning up patches will follow this.
    Signed-off-by: default avatarMasahiro Yamada <yamada.m@jp.panasonic.com>
    Reviewed-by: default avatarSimon Glass <sjg@chromium.org>
    e02ee254
Makefile.spl 7.05 KB