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?
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