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

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Date:   Thu, 9 Mar 2023 13:15:49 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Timur Tabi <timur@...nel.org>
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

Hi

Am 08.03.23 um 17:26 schrieb Timur Tabi:
> 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.

I'm preparing an update to this series. The string will be allocated and 
freed with kstrdup() and kfree(). So these issues should be resolved then.

Best regards
Thomas


-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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