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

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Message-ID: <CAMuHMdU6XD_tqXaf4-h9KeC58XDOodUWa0d-Wmp6zcr2BHTA1w@mail.gmail.com>
Date: Tue, 20 May 2025 15:09:55 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Marcus Folkesson <marcus.folkesson@...il.com>, 
	Javier Martinez Canillas <javierm@...hat.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

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 ;-)

The alternative is to just drop the old symbols, and ignore current users.
Which is not that uncommon...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds