[U-Boot] [PATCH v2 3/4] kconfig: switch to single .config configuration

[Masahiro YAMADA]

Hi Simon,


2015-02-21 4:20 GMT+09:00 Simon Glass <sjg at chromium.org>:
> Hi Stephen,
>
> On 19 February 2015 at 14:13, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> On 02/19/2015 12:55 AM, 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.
>>>
>>> [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.
>>>
>>> [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.
>>>
>>> [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.
>>
>>
>>> diff --git a/arch/arm/cpu/armv7/tegra-common/Kconfig
>>> b/arch/arm/cpu/armv7/tegra-common/Kconfig
>>> index 0de13ae..c9e8919 100644
>>> --- a/arch/arm/cpu/armv7/tegra-common/Kconfig
>>> +++ b/arch/arm/cpu/armv7/tegra-common/Kconfig
>>> @@ -26,7 +26,7 @@ config SYS_MALLOC_F_LEN
>>>         default 0x1800 if SYS_MALLOC_F
>>>
>>>   config USE_PRIVATE_LIBGCC
>>> -       default y if SPL_BUILD
>>> +       default y
>>>
>>>   config DM
>>>         default y if !SPL_BUILD
>>
>>
>> I think the above patch demonstrates the problem very nicely; it changes the
>> semantics from having CONFIG_USE_PRIVATE_LIBGCC enabled only in SPL build to
>> having it enabled everywhere. While that particular change shouldn't be an
>> issue, I think that requiring that all config options to have the same value
>> in main/SPL/TPL will be. For example, how do we disabled MMC support in SPL?
>> We have to introduce separate CONFIG_MMC and CONFIG_SPL_MMC don't we? That
>> doesn't seem any better than having separate defconfig files for
>> SPL/non-SPL, or using ifdefs in a single defconfig file. What happened to
>> the ability of one defconfig file to include another, so options could be
>> shared between the two?
>
> We use separate options for normal and SPL now. Currently we have
> CONFIG_SPL_MMC_SUPPORT. So it already works this way.
>
> If we can move to a world where SPL and U-Boot are more similar that
> will be good.
>
> What I don't understand about this change is why we cannot have
> 'default y if SPL_BUILD' in a rule if we want to. It seems like that
> would be useful.


CONFIG_SPL_BUILD is not defined in Kconfig any more,
i.e. we can not use the "if SPL_BUILD" conditonal.

It is given when descending into the spl directory, like the pre-kconfig build.

Here in scripts/Makefile.spl

-include include/config/auto.conf
-include $(obj)/include/autoconf.mk

KBUILD_CPPFLAGS += -DCONFIG_SPL_BUILD
ifeq ($(CONFIG_TPL_BUILD),y)
KBUILD_CPPFLAGS += -DCONFIG_TPL_BUILD
endif





-- 
Best Regards
Masahiro Yamada