FYI: Changing contents and compression for `config` file in CBFS

[Julius Werner]

I don't know if anybody cares about this, so I thought I'd send an
email just in case:

I'd like to change the format of the `config` file that automatically
gets included in CBFS: right now it just contains the output of
Kconfig's `savedefconfig` command, i.e. the minimal `.config` file
that is needed to reproduce the full config (with all the default
options and options that get `select`ed by something else excluded).
This is a problem if you want to use the file to just check if a
certain option was enabled in the image or not, since many options are
enabled by default in certain cases, and the rules for when exactly
what is the default setting can be complicated and change frequently.

I would like to have a `config` file that I can just extract and then
grep for a certain CONFIG_XXX=y to check if that config was enabled or
not. So I'm changing the generation of the `config` file to instead
include all options that are not set to false in Kconfig (i.e.
basically the full coreboot `.config` file, just with comments
removed). Since this makes the file quite a bit bigger I think we
should also start to compress it with LZMA, as it's only meant to be
re-extracted with cbfstool anyway so there seems to be no reason not
to. (Or does anyone care strongly about being able to read the config
file when opening the raw image with a hex editor?)

I've uploaded this CL as https://review.coreboot.org/69710 . Please
comment there if anyone has a concern about this change.

[Martin Roth]

Seems reasonable to me.  Thanks Julius.

Martin


Nov 16, 2022, 19:12 by [e-mail]:
> I don't know if anybody cares about this, so I thought I'd send an
> email just in case:
>
> I'd like to change the format of the `config` file that automatically
> gets included in CBFS: right now it just contains the output of
> Kconfig's `savedefconfig` command, i.e. the minimal `.config` file
> that is needed to reproduce the full config (with all the default
> options and options that get `select`ed by something else excluded).
> This is a problem if you want to use the file to just check if a
> certain option was enabled in the image or not, since many options are
> enabled by default in certain cases, and the rules for when exactly
> what is the default setting can be complicated and change frequently.
>
> I would like to have a `config` file that I can just extract and then
> grep for a certain CONFIG_XXX=y to check if that config was enabled or
> not. So I'm changing the generation of the `config` file to instead
> include all options that are not set to false in Kconfig (i.e.
> basically the full coreboot `.config` file, just with comments
> removed). Since this makes the file quite a bit bigger I think we
> should also start to compress it with LZMA, as it's only meant to be
> re-extracted with cbfstool anyway so there seems to be no reason not
> to. (Or does anyone care strongly about being able to read the config
> file when opening the raw image with a hex editor?)
>
> I've uploaded this CL as https://review.coreboot.org/69710 . Please
> comment there if anyone has a concern about this change.
> _______________________________________________
> coreboot mailing list -- [e-mail]
> To unsubscribe send an email to [e-mail]