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

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Message-ID: <CAOZdJXUtkyg5Gv3HYCK-U1pQpY0_QBk99wtqUvz5RVy2W3Ak9w@mail.gmail.com>
Date:   Mon, 6 Mar 2023 14:04:54 -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, timur@...nel.org,
        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 Mon, Mar 6, 2023 at 10:01 AM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>
> Assume that the driver does not own the option string or its substrings
> and hence duplicate the option string for the video mode. The driver only
> parses the option string once as part of module initialization, so use
> a static buffer to store the duplicated mode option. Linux automatically
> frees the memory upon releasing the module.

So after module_init is finished, mode_option_buf[] no longer exists?

> +                       static char mode_option_buf[256];
> +                       int ret;
> +
> +                       ret = snprintf(mode_option_buf, sizeof(mode_option_buf), "%s", opt);
> +                       if (WARN(ret < 0, "fsl-diu-fb: ignoring invalid option, ret=%d\n", ret))
> +                               continue;
> +                       if (WARN(ret >= sizeof(mode_option_buf), "fsl-diu-fb: option too long\n"))
> +                               continue;
> +                       fb_mode = mode_option_buf;

If so, then I'm not sure that's going to work.  fb_mode is used after
module_init, in install_fb(), which is called by fsl_diu_probe().