linux-kernel - Re: [PATCH] drm/sitronix: Fix broken backwards-compatibility layer

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Message-ID: <87plg3nz9g.fsf@minerva.mail-host-address-is-not-set>
Date: Tue, 20 May 2025 16:16:27 +0200
From: Javier Martinez Canillas <javierm@...hat.com>
To: Thomas Zimmermann <tzimmermann@...e.de>, Geert Uytterhoeven
 <geert@...ux-m68k.org>
Cc: Marcus Folkesson <marcus.folkesson@...il.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/sitronix: Fix broken backwards-compatibility layer

Thomas Zimmermann <tzimmermann@...e.de> writes:

> Hi
>
> Am 20.05.25 um 15:09 schrieb Geert Uytterhoeven:
>> Hi Thomas,
>>
>> On Tue, 20 May 2025 at 15:04, Thomas Zimmermann <tzimmermann@...e.de> wrote:
>>> Am 20.05.25 um 14:40 schrieb Geert Uytterhoeven:
>>>> When moving the Sitronix DRM drivers and renaming their Kconfig symbols,
>>>> the old symbols were kept, aiming to provide a seamless migration path
>>>> when running "make olddefconfig" or "make oldconfig".
>>>>
>>>> However, the old compatibility symbols are not visible.  Hence unless
>>>> they are selected by another symbol (which they are not), they can never
>>>> be enabled, and no backwards compatibility is provided.
>>>>
>>>> Fix this by making them visible, and inverting the selection logic.
>>>> Add comments to make it clear why there are two symbols with the same
>>>> description.
>>> These symbols were only meant for variants of 'make oldconfig' to pick
>>> up th enew symbols. They where never for being selected manually.
>> But that pick-up does not work, unfortunately...
>> (I know, I had one of them enabled in one of my configs ;-)
>
> I see.
>
>>
>> The alternative is to just drop the old symbols, and ignore current users.
>> Which is not that uncommon...
>
> If there's no easy fix for the current setup, I'd prefer removing the 
> old symbols.
>

I agree. When this was discussed, I argued that we should just remove the
old symbols and let kernel packagers to deal with it. As Geert said, it's
not uncommon for Kconfig symbols names to change over time...

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat