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

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Date:	Mon, 1 Aug 2011 13:14:36 -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 12:48 PM, Kyle Moffett <kyle@...fetthome.net> wrote:
> 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?
I'm working on that, but this is a real mess :)

> 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?
>
not I directly forsee.

 - Arnaud

> Cheers,
> Kyle Moffett
>
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