[U-Boot] [PATCH v3 5/7] kconfig: switch to single .config configuration

[Simon Glass]

Hi Scott,

On Feb 23, 2015 6:23 PM, "Scott Wood" <scottwood at freescale.com> wrote:
>
> On Fri, 2015-02-20 at 14:24 +0900, Masahiro Yamada wrote:
> > 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.
>
> Sharing can happen in the defconfig with "+S:"...
>
> What sort of dependencies are people wanting?  Would it be possible to
> modify kconfig to import SPL .config into the main config (or vice
> versa?) with a name prefix so that dependencies could happen, without
> sacrificing the ability to set symbols independently?
>
> Or as Ian suggested, have only the main config be user-editable, but
> still let select/depends turn certain things on/off for the
> auto-generated SPL config.
>
> > [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 cbdd9a9737cc (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.
>
> How about defconfig fragments?  Instead of having script infrastructure
> specifically for CONFIG_SPL_FEL, merge a fragment containing
> "+S:CONFIG_SPL_FEL".
>
> > [3] Kconfig files are getting ugly and difficult to understand.
> >   Commit b724bd7d6349 (dm: Kconfig: Move CONFIG_SYS_MALLOC_F_LEN to
> >   Kconfig) has sprinkled "if !SPL_BUILD" over the Kconfig files.
>
> It seems like the root cause of this sprinkling is wanting to use
> default y to avoid touching a bunch of defconfig files, but not wanting
> to do the default y at the toplevel Kconfig.  Maybe better tooling for
> bulk defconfig updates would help.  In any case, couldn't you do
> CONFIG_SPL_DM currently, by making DM depend on "!SPL_BUILD || SPL_DM",
> without fundamentally changing the SPL kconfig infrastructure?
>
> Why do symbols like LOCALVERSION and CC_OPTIMIZE_FOR_SIZE depend on !
> SPL_BUILD?
>
> > [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 had been hoping that the split configs would let us get rid of many of
> the CONFIG_SPL_* options that we already have.

As Masahiro says this will happen as we remove one by one the various
SPL special cases. For example, when driver model supports SPL and
U-Boot then we won't need that option - you will either use driver
model (or not) for both. I suspect other options will go the same way.

But if things are split into multiple configs it is really hard to
compare them and keep them in sync.

Once the dust settles I will be sending a series to remove the special
cases around CONFIG_SPL_DM.

>
> How will TPL be handled?  Are you going to duplicate all the SPL
> symbols?  Or just avoid ever kconfigizing them?
>
> >  - 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.
>
> How is uncmd_spl better than "!SPL_BUILD"?

Regards,
Simon