linux-kernel - Re: [PATCH] Remove remaining references of CONFIG_GENERIC

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Message-ID: <CACqU3MUoxSNmcYsSF4zOTgADdedb7TcciPuBPMviG02M5oUPDQ@mail.gmail.com>
Date:	Mon, 1 Aug 2011 12:08:08 -0400
From:	Arnaud Lacombe <lacombar@...il.com>
To:	Kyle Moffett <kyle@...fetthome.net>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Zoltan Devai <zdevai@...il.com>, linux-kernel@...r.kernel.org,
	chris@...kel.net, linux-am33-list@...hat.com, trivial@...nel.org,
	user-mode-linux-devel@...ts.sourceforge.net, cmetcalf@...era.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-kbuild <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH] Remove remaining references of CONFIG_GENERIC_TIME

Hi,

On Mon, Aug 1, 2011 at 11:15 AM, Kyle Moffett <kyle@...fetthome.net> wrote:
> On Mon, Aug 1, 2011 at 11:04, Arnaud Lacombe <lacombar@...il.com> wrote:
>> Hi,
>>
>> On Mon, Aug 1, 2011 at 7:27 AM, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>>> On Mon, Aug 1, 2011 at 12:14, Russell King - ARM Linux
>>>>>[...]
>>>>>
>>>>> Doesn't kconf error out when trying to select a non-existent symbol?
>>>>
>>>> Nope.
>>>
>>> You're right. So that's a bug.
>>>
>> depends on what you are trying to achieve and what the problem is.
>>
>> Internally kconfig will create a dummy symbol when it encounter a
>> missing symbol so that arch/arm/Kconfig can reference a symbol which
>> will be fully defined later on. I do not think you want to forward
>> decl all the symbol which can be used. That'd be a mess. That said, we
>> can come with a form of symbol deprecation that would error-out when
>> used.
>
> Would it be possible instead to make Kconfig go through all the symbols
> after everything is processed and identify any remaining "dummy symbols"
> which were not actually declared anywhere?
>
this is software, everything is possible.

> Right now if you typo a "select" statement you get no warnings that you
> are selecting something that does not exist, which is probably a cause
> of many kinds of errors beyond this particular one.
>
d'oh! ... I'm not sure we want that. Dummy symbol are heavily used
internally, a trivial implementation[0] triggered:

% make REGENERATE_PARSERS=y alldefconfig 2>&1 | grep 'defined without
type' | wc -l
817

Moreover, this approach is deemed to fail. The current symbol
namespace is tied to an arch, so whenever you do:

arch/arm/Kconfig:
config FOO
    bool

config BAZ
    bool

drivers/cpufreq/Kconfig
config BAR
    depends on ARM && FOO
    select BAZ

You will end up triggering the warning for every ARCH != ARM...

 - Arnaud

[0]: or rather a fix as we currently only do the check for symbol linked to menu
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