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From: Jani Nikula <jani.nikula@linux.intel.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>, Maarten Lankhorst
 <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>,
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 Daniel Vetter <daniel@ffwll.ch>, dri-devel@lists.freedesktop.org,
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 <linux-renesas-soc@vger.kernel.org>, Masahiro Yamada
 <masahiroy@kernel.org>, linux-kbuild <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH 00/11] drm: Restore helper usability
In-Reply-To: <CAMuHMdXCL-gbKr6mUBPWONtRjz=X0vZQgiS=02WXXSFf67yBww@mail.gmail.com>
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Date: Mon, 22 Apr 2024 20:14:53 +0300
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On Mon, 22 Apr 2024, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Arnd,
>
> CC kbuild
>
> On Mon, Apr 22, 2024 at 3:55=E2=80=AFPM Arnd Bergmann <arnd@arndb.de> wro=
te:
>> I'm not sure where this misunderstanding comes from, as you
>> seem to be repeating the same incorrect assumption about
>> how select works that Maxime wrote in his changelog. To clarify,
>> this works exactly as one would expect:
>>
>> config HELPER_A
>>        tristate
>>
>> config HELPER_B
>>        tristate
>>        select HELPER_A
>>
>> config DRIVER
>>        tristate "Turn on the driver and the helpers it uses"
>>        select HELPER_B # this recursively selects HELPER_A
>>
>> Whereas this one is broken:
>>
>> config FEATURE_A
>>        tristate "user visible if I2C is enabled"
>>        depends on I2C
>>
>> config HELPER_B
>>        tristate # hidden
>>        select FEATURE_A
>>
>> config DRIVER
>>        tristate "This driver is broken if I2C is disabled"
>>        select HELPER_B
>
> So the DRIVER section should gain a "depends on I2C" statement.

Why should DRIVER have to care that HELPER_B needs either FEATURE_A or
I2C? It should only have to care about HELPER_B. And if the dependencies
of FEATURE_A or HELPER_B later change, that's their business, not
DRIVER's.


BR,
Jani.

>
> Yamada-san: would it be difficult to modify Kconfig to ignore symbols
> like DRIVER that select other symbols with unmet dependencies?
> Currently it already warns about that.
>
> Handling this implicitly (instead of the current explict "depends
> on") would have the disadvantage though: a user who is not aware of
> the implicit dependency may wonder why DRIVER is invisible in his
> config interface.

--=20
Jani Nikula, Intel