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