What's wrong with changing * _defconfig when working with Linux kernel sources

    Following the traces of my first publication, I want to make a short note about changing the i386_defconfig or x86_64_defconfig files included in the Linux kernel source package.

    In the comments on that publication, users (in particular ValdikSS ) were interested in why not editing .config? On the scale of the comment, I could not give a detailed answer there.

    So, let's start with the difference between .config and * _defconfig. Attentive user typing a team
    wc -l .config arch/x86/configs/{i386,x86_64}_defconfig

    3972 .config
    369 arch / x86 / configs / i386_defconfig
    368 arch / x86 / configs / x86_64_defconfig
    4709 total

    can easily detect that the file difference is about 10 (!) times.

    What does it do make *_defconfig? Actually nothing super special. Important actions are listed below:
    • Removes options that are outdated or missing in the current kernel version.
    • Builds a dependency tree for an option
    • Applies default rules to all options that were specified in the default configuration and by dependencies
    • Translates all this into a .config file

    Reverse action for the most inquisitive
    The reverse action is performed make savedefconfig, here a little more detail.

    Therefore, it is not just a copy of the file.

    Returning to editing the original version of * _defconfig. What are the benefits?
    • Minimum changes that need to be made, the rest will be done for us by scripts
    • You can always see the difference with a stable base ( git diff)

    • Inconvenient in rare cases git bisect
    • Need your own local brunch (which can be both an advantage and a disadvantage)

    In the list I already hinted that the standard practice of editing files in Git involves creating your own brunch. There we accumulate our own changes. For me, the advantages outweighed the disadvantages, so I do not see anything reprehensible in editing * _defconfig.

    What are your practices?

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