linux-kernel - Re: [PATCH 22/99] fbdev/fsl-diu-fb: Duplicate video-mode option string

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Message-ID: <CAOZdJXWGNBHMPRmkBYeVL31=Q0Y=fLa8RG0KS668xQ9ozD+Xtg@mail.gmail.com>
Date:   Wed, 8 Mar 2023 10:26:34 -0600
From:   Timur Tabi <timur@...nel.org>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     deller@....de, paulus@...ba.org, benh@...nel.crashing.org,
        linux@...linux.org.uk, pjones@...hat.com, adaplas@...il.com,
        s.hauer@...gutronix.de, shawnguo@...nel.org, mbroemme@...mpq.org,
        thomas@...ischhofer.net, James.Bottomley@...senpartnership.com,
        spock@...too.org, sudipm.mukherjee@...il.com,
        teddy.wang@...iconmotion.com, geert+renesas@...der.be,
        corbet@....net, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 22/99] fbdev/fsl-diu-fb: Duplicate video-mode option string

On Tue, Mar 7, 2023 at 2:28 AM Thomas Zimmermann <tzimmermann@...e.de> wrote:
> > So after module_init is finished, mode_option_buf[] no longer exists?
>
> Does the __init attribute on a function affect the static variables in
> that function?

That is an excellent question.

https://stackoverflow.com/questions/64558614/what-happens-to-local-static-identifiers-in-init-function

I don't think the compiler is naturally aware of whatever section a
variable or function is placed in, so it can't really know that
mode_option_buf[] is suppose to have a limited lifetime.

Either way, the code seems wrong.  If mode_option_buf[] is marked as
__initdata, then it will disappear before the probe() function is
called.

If mode_option_buf[] remains resident, then we are wasting 256 bytes.