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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 6 Mar 2023 17:13:34 +0100
Message-ID: <CAMuHMdVDr19p3GtR4n_hJAtc_RX+VJwVfU1Mzvtka9er+WS8bg@mail.gmail.com>
Subject: Re: [PATCH 11/99] fbdev/aty: Duplicate video-mode option string
To:     Thomas Zimmermann <tzimmermann@suse.de>
Cc:     deller@gmx.de, paulus@samba.org, benh@kernel.crashing.org,
        linux@armlinux.org.uk, pjones@redhat.com, timur@kernel.org,
        adaplas@gmail.com, s.hauer@pengutronix.de, shawnguo@kernel.org,
        mbroemme@libmpq.org, thomas@winischhofer.net,
        James.Bottomley@hansenpartnership.com, spock@gentoo.org,
        sudipm.mukherjee@gmail.com, teddy.wang@siliconmotion.com,
        geert+renesas@glider.be, corbet@lwn.net,
        linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
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Hi Thomas,

Thanks for your patch!

On Mon, Mar 6, 2023 at 5:00 PM Thomas Zimmermann <tzimmermann@suse.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.

Are you sure about that?
All of this code is inside "#ifndef MODULE".
In the aty128fb case, the function is not marked __init.
Enabling these 3 drivers adds 3x256 bytes of static buffer, more
if you enable more fbdev drivers.

> Done in preparation of switching the driver to struct option_iter and
> constifying the option string.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

> --- a/drivers/video/fbdev/aty/aty128fb.c
> +++ b/drivers/video/fbdev/aty/aty128fb.c
> @@ -1723,7 +1723,17 @@ static int aty128fb_setup(char *options)
>                         continue;
>                 }
>  #endif /* CONFIG_PPC_PMAC */
> -               mode_option = this_opt;
> +               {
> +                       static char mode_option_buf[256];
> +                       int ret;
> +
> +                       ret = snprintf(mode_option_buf, sizeof(mode_option_buf), "%s", this_opt);
> +                       if (WARN(ret < 0, "aty128: ignoring invalid option, ret=%d\n", ret))
> +                               continue;
> +                       if (WARN(ret >= sizeof(mode_option_buf), "aty128fb: option too long\n"))
> +                               continue;
> +                       mode_option = mode_option_buf;
> +               }
>         }
>         return 0;
>  }
eturn 0;
>  }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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