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References: <20240212170423.2860895-1-andriy.shevchenko@linux.intel.com> <20240212170423.2860895-11-andriy.shevchenko@linux.intel.com>
In-Reply-To: <20240212170423.2860895-11-andriy.shevchenko@linux.intel.com>
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 15 Feb 2024 11:40:44 +0100
Message-ID: <CAMuHMdVtqWBi4Y1tj74m4V4kp-3cFe_FphKKeY7zOkrbMVkKRg@mail.gmail.com>
Subject: Re: [PATCH v2 10/15] auxdisplay: linedisp: Provide a small buffer in
 the struct linedisp
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, 
	Andy Shevchenko <andy@kernel.org>, Rob Herring <robh+dt@kernel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, 
	Robin van der Gracht <robin@protonic.nl>, Paul Burton <paulburton@kernel.org>
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Hi Andy,

On Mon, Feb 12, 2024 at 6:04=E2=80=AFPM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
> There is a driver that uses small buffer for the string, when we
> add a new one, we may avoid duplication and use one provided by
> the line display library. Allow user to skip buffer pointer when
> registering a device.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Thanks for your patch!

> --- a/drivers/auxdisplay/line-display.c
> +++ b/drivers/auxdisplay/line-display.c
> @@ -330,8 +330,8 @@ int linedisp_register(struct linedisp *linedisp, stru=
ct device *parent,
>         linedisp->dev.parent =3D parent;
>         linedisp->dev.type =3D &linedisp_type;
>         linedisp->ops =3D ops;
> -       linedisp->buf =3D buf;
> -       linedisp->num_chars =3D num_chars;
> +       linedisp->buf =3D buf ? buf : linedisp->curr;
> +       linedisp->num_chars =3D buf ? num_chars : min(num_chars, LINEDISP=
_DEFAULT_BUF_SZ);

I think it would be safer to return an error if buf =3D=3D NULL and
num_chars < LINEDISP_DEFAULT_BUF_SZ.
Else a careless driver that doesn't check linedisp->num_chars might
overflow the buffer.

>         linedisp->scroll_rate =3D DEFAULT_SCROLL_RATE;
>
>         err =3D ida_alloc(&linedisp_id, GFP_KERNEL);

Gr{oetje,eeting}s,

                        Geert

--=20
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k=
org

In personal conversations with technical people, I call myself a hacker. Bu=
t
when I'm talking to journalists I just say "programmer" or something like t=
hat.
                                -- Linus Torvalds