linux-kernel - Re: [PATCH 00/11] drm: Restore helper usability

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Date: Mon, 22 Apr 2024 20:14:53 +0300
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>, Arnd Bergmann <arnd@...db.de>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, Dave Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Linux-Renesas
 <linux-renesas-soc@...r.kernel.org>, Masahiro Yamada
 <masahiroy@...nel.org>, linux-kbuild <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH 00/11] drm: Restore helper usability

On Mon, 22 Apr 2024, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Hi Arnd,
>
> CC kbuild
>
> On Mon, Apr 22, 2024 at 3:55 PM Arnd Bergmann <arnd@...db.de> wrote:
>> 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.

-- 
Jani Nikula, Intel