On Wed, 2015-02-25 at 15:14 +0900, Masahiro Yamada wrote:
> Hi Scott,
>
>
> On Tue, 24 Feb 2015 18:17:59 -0600
> Scott Wood <scottw...@freescale.com> wrote:
>
> > On Tue, 2015-02-24 at 16:20 +0900, Masahiro Yamada wrote:
> > > Hi Scott,
> > >
> > >
> > > On Mon, 23 Feb 2015 19:22:51 -0600
> > > Scott Wood <scottw...@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:"...
> > >
> > > Yes, it can as for "make *_defconfig".
> > >
> > > If we modify some options in .config for example by "make menuconfig",
> > > we also modify some in spl/.config correspondingly.
> > >
> > > Users are responsible for configure .config and spl/.config in sync
> > > in the sane combination.
> > >
> > >
> > >
> > > > 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?
> > >
> > > To have independent symboles coexist in a single .config,
> > > I can only suggest to duplicate options like
> > > CONFIG_FOO=0x100
> > > CONFIG_SPL_FOO=0x200
> > > CONFIG_TPL_FOO=0x300
> >
> > What I meant was a way to keep the configs separate, but automatically
> > import the CONFIG_FOO from the SPL .config as CONFIG_SPL_FOO (or some
> > other prefix that doesn't conflict with SPL-specific options).
>
> What is the benefit of doing this?
So that you can express dependencies in the main U-Boot on SPL symbols,
which you said was one of the problems that motivated this change.
> > > > 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.
> > >
> > > I guess it is possible for boolean options,
> > > but impossible to set hex/int options independently.
> >
> > How many hex/int options are there, that need to be different in SPL
> > versus the main U-Boot? Having a few CONFIG_SPL_xxx for those is better
> > than having a bunch.
>
> OK.
> But, I do not think we need to tweak the Kconfig just for saving boolean
> options.
Most options are boolean (especially if you ignore hardware description
that isn't going to differ between SPL and non-SPL). I think it makes a
lot of sense to not want to duplicate them, and especially to not
complicate each place that ifdefs on the symbol by having to check for
SPL.
> > > BTW, Ian's idea had been already achieved by include/config_uncmd_spl.h
> >
> > So, the answer is to avoid kconfig and go back to using the preprocessor
> > for configuration? :-(
>
> I am not saying I prefer the preprocessor.
>
> Indeed, include/config_uncmd_spl.h is ugly,
> so I'd like to propose a better solution.
>
> If we introduce CONFIG_SPL_DM, for example, the ifdef conditional in source
> files
> will be like this:
>
> #if (!defined(CONFIG_SPL_BUILD) && defined(CONFIG_DM)) || \
> (defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_DM))
>
> [Driver Model Code]
>
> #else
> [Non Driver Model Code]
> #endif
>
> This is too ugly to be written in each conditional.
That's not what I was suggesting.
I was suggesting something like:
config DM
bool "Enable Driver Model"
depends on !SPL_BUILD || SPL_DM
...
Then the ifdef would just be
#ifdef CONFIG_DM
[Driver Model Code]
#else
[Non Driver Model Code]
#endif
> > > > > [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".
> > >
> > > Do you mean something like this?
> > > U-boot proper : common/.config + .config
> > > SPL : common/.config + spl/.config
> > > TPL : common/.config + tpl/.config
> >
> > No, I meant having a fragment containing only "+S:CONFIG_SPL_FEL" that
> > could be merged into any other config.
>
> So, the fragment is something like the _common_ .config, right?
The fragment would be part of a library of common config tweaks that
users can apply -- providing similar convenience as _felconfig but with
generic infrastructure.
> > > > > [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.
> > > >
> > > > How will TPL be handled? Are you going to duplicate all the SPL
> > > > symbols? Or just avoid ever kconfigizing them?
> > >
> > > Not all, but I expect some duplicated CONFIG_TPL_* such as
> > > CONFIG_TPL_TEXT_BASE.
> >
> > I'm not talking about TEXT_BASE. I'm talking about stuff like this:
>
> We have to add some CONFIG_TPL_*, but we will just have 20.
Just? And how much makefile crud to check for those options when
building? To achieve what?
> > If you redefine TPL to mean SPL that doesn't use certain code, you'll
> > end up with targets that have TPL but no SPL. Are you sure this is
> > simplifying anything?
>
> Sorry, I can't get it.
> What I expect is like follows:
>
> CONFIG_TPL still depends on CONFIG_SPL.
>
> We have three options for the boot procedure:
>
> [1] U-Boot-proper (CONFIG_SPL is not defined)
>
> [2] SPL + U-Boot-proper (CONFIG_SPL is defined)
>
> [3] TPL + SPL + U-Boot-proper (CONFIG_SPL and CONFIG_TPL are defined)
>
>
> The image size: TPL < SPL < U-Boot-proper
>
> Driver Model and some other features are available on SPL if CONFIG_SPL_* is
> defined.
>
> Almost no systematic infrastructure is available on TPL, so we will have
> very small number of CONFIG_TPL_*.
So instead of CONFIG_TPL_* we'd have more hardcoded makefile hackery to
disable things in TPL -- and we'd have to duplicate that hackery for
SPLs that are just as small as what you're now calling TPL, if you're
not going to allow TPL without SPL.
-Scott
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