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

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Message-ID: <CAGZ=bqLHjzpKQP63dnSK0fML2ZycmfFnSbiApV4naMCN_UrZdg@mail.gmail.com>
Date:	Mon, 1 Aug 2011 12:48:19 -0400
From:	Kyle Moffett <kyle@...fetthome.net>
To:	Arnaud Lacombe <lacombar@...il.com>
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

On Mon, Aug 1, 2011 at 12:08, Arnaud Lacombe <lacombar@...il.com> wrote:
> 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:
>>> 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...

Perhaps that's an argument for building a single Kconfig namespace?
At the very least, most of the architecture-generic warnings could be
worked around with trivial predeclarations in an "arch/Kconfig" file:

config ARM
        bool
[...]
config X86
        bool

There's probably technical issues that I'm missing that would make
that inordinately painful, but I can't see them right now... any ideas?

Cheers,
Kyle Moffett
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