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authorMasahiro Yamada <yamada.m@jp.panasonic.com>2015-02-24 22:26:20 +0900
committerTom Rini <trini@ti.com>2015-02-24 17:06:23 -0500
commite02ee2548afe22f7d197b89df2ae7bd72f1df630 (patch)
tree1c3c0dfbdd5bca4a88689aa4aafb308e8c872035 /dts/Kconfig
parent66afaef22889e2685aa500c047b66ac003eea264 (diff)
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kconfig: switch to single .config configuration
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. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Reviewed-by: Simon Glass <sjg@chromium.org>
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