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Add a writeup of how the kernel config project designed to behave when migrating kernel versions. Signed-off-by: Tycho Andersen <tycho@docker.com>
39 lines
1.7 KiB
Markdown
39 lines
1.7 KiB
Markdown
## kernel config project
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The intent of the kernel config project is to demonstrate a better way to
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handle kernel config. Specifically:
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* support for arch and version specific config
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* make diffs as readable as possible
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* ensure that all of our config settings are kept after oldconfig
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We achieve the goals by:
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* having version-specific config in separate files, which are automatically
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merged
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* only keeping track of visible symbols, only keeping track of a delta from
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defconfig, and keeping symbols sorted alphabetically
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* checking after a `make oldconfig` in the kernel, that all of our symbols are
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set as we want them to be
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The bulk of this work happens in makeconfig.sh, which merges the configs (and
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checks that the resulting config is okay).
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One important piece is generating a kernel config for a new version. There are
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a few cases:
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* A new kconfig symbol is introduced that we want to set a non-default value
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of: in this case, we introduce a new `kernel_config.${VERSION}` file, and set
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the value to what we want to set it to
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* A config symbol that was no-default before become the default: in this case,
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we would move the non-default setting to version specific files for all of
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the other versions, and not set anything for this new kernel, since what we
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want is now the default.
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* A symbol we want to set is removed (or renamed), similar to the above, we
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simply move the old symbol name to version specific files for older kernels
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and put the new symbol name (if it exists) in the new version specific file
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When dropping support for an old kernel version, we just delete that version
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specific file, and promote any option that is present in all other versions to
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the common config file.
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