[RFC PATCH] Kconfig: Enable Kconfig fragments to be used for defconfig

[Daniel Walker]

On Tue, 2010-07-13 at 17:21 -0600, Grant Likely wrote:
> On Tue, Jul 13, 2010 at 5:14 PM, Daniel Walker <dwalker at codeaurora.org> wrote:
> > On Tue, 2010-07-13 at 17:04 -0600, Grant Likely wrote:
> >
> >> - I haven't figured out a way for the fragment to force an option to
> >>   be "n", or to set a value, for example "CONFIG_LOG_BUF_SHIFT=16".
> >>   This may require changing the syntax.
> >> - It still doesn't resolve dependencies.  A solver would help with this.
> >>   For the time being I work around the problem by running the generated
> >>   config through 'oldconfig' and looking for differences.  If the files
> >>   differ (ignoring comments and generateconfig_* options) after oldconfig,
> >>   then the <board>_defconfig target returns a failure.  (but leaves the
> >>   new .config intact so the user can resolve it with menuconfig).  This
> >>   way at least the user is told when a Kconfig fragment is invalid.
> >
> > The solver would fix the whole issues with the defconfigs , we wouldn't
> > need this Kconfig change .. From my perspective we shouldn't be fooling
> > around with anything but the solver approach ..
> 
> The solver would complement Kconfig fragments, but it doesn't
> implement all the functionality.  For instance, it doesn't help a
> board config picking up a bunch of options from an SoC or Architecture
> config file, especially things that are developer/maintainer choices
> as opposed to hard requirements).  Solver on its own is an incremental
> improvement over what we currently have, but it doesn't solve the
> whole problem.

I don't understand what your saying here.. Imagine a defconfig that you
have now only drastically smaller. The solver picks the stuff that
doesn't exist already in the defconfig. You would just apply the solver
to whatever is in the defconfig.

Then that allows us to keep the current defconfig format without mass
converting to something else. It's would also be built on a solver that
helps with other issues within Kconfig.

> > It just doesn't feel like Kconfig was meant to do this, it feel like
> > somewhat of an abuse ..
> 
> Why?  It uses the Kconfig language itself to specify additional
> constraints on the final configuration.  Seems to be the essence of
> elegance to me.  :-)

To my mind the only problem with the current defconfig formatting is the
size of the files. If those files are 5-10 lines instead of 2000 lines,
then I think the readability problem isn't really an issue any more..

The point of using Kconfig was the readability..

Daniel

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