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Date: Sun, 8 Aug 2010 17:57:12 +0200
From: Sam Ravnborg <sam@ravnborg.org>
To: Arve Hj?nnev?g <arve@android.com>
Cc: Michal Marek <mmarek@suse.cz>,
        Linus Torvalds <torvalds@linux-foundation.org>, JBeulich@novell.com,
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        zippel@linux-m68k.org, linux-kbuild@vger.kernel.org,
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Subject: Re: [GIT] kbuild: kconfig changes
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On Fri, Aug 06, 2010 at 09:43:24PM -0700, Arve Hj?nnev?g wrote:
> On Fri, Aug 6, 2010 at 9:01 PM, Sam Ravnborg <sam@ravnborg.org> wrote:
> >>
> >> This change prevents some the minimal defconfig options from working.
> >> Specifically our usb gadget drivers do not get set.
> >
> > Can you help me reproduce this?
> >
> > I have found an issue with choice values in combination with
> > tristate logic that fails. I hope this is something similar.
> >
> 
> It is probably the same problem. The gadget driver that was not set is
> not buildable as a module (it is not in the mainline kernel). If I
> select another gadget driver instead it just gets changed to build as
> a module instead.
> 
> If you create a file, arch/arm/configs/test_defconfig with the following:
> CONFIG_MODULES=y
> CONFIG_USB_GADGET=y
> CONFIG_USB_MASS_STORAGE=y
> 
> then "make test_defconfig" results in .config having:
> CONFIG_USB_MASS_STORAGE=m
> 
>  (at least if you are set up to compile for arm)

Thanks Arve.

I have it reproduced now with a simple Kconfig:

$ cat Kconfig
config M
	def_bool y
	option modules

choice
	prompt "choice list"

config A
	tristate "a"

config B
	tristate "b"

endchoice

$cat defconfig
CONFIG_M=y
CONFIG_A=y
# CONFIG_B is not set


If I do:

    $scripts/kconfig/conf --defconfig=defconfig Kconfig

with the above input the resulting .config is OK.

But If I drop the line:

    # CONFIG_B is not set

in the defconfig file then I end with CONFIG_A set to m.
And this is not as expected - I cannot see why it should matter
if we specify the value of B or not.

What we see here is that savedefconfig trigger a bug in the
other part of kconfig - a bug which was not exposed before.

The reason why your patch cured it was that we then no
longer triggered the bug (at least I guess so I did not look to close).

I will look into this as time permits. I assume the fix is simple
when I find the reason.

I fear it is in menu_finalize() and that part of kconfig I have
not yet understood.

	Sam