linux-kernel - Re: [PATCH 08/10] spi: rzv2m-csi: Improve data types and alignment

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Message-ID: <CAMuHMdXd5-+2F0yG70urKe5xdwa9K_dg5t_t+UzQ9pJ+eD8FSA@mail.gmail.com>
Date:   Mon, 17 Jul 2023 11:44:49 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Fabrizio Castro <fabrizio.castro.jz@...esas.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH 08/10] spi: rzv2m-csi: Improve data types and alignment

Hi Fabrizio,

Thanks for your patch!

On Sat, Jul 15, 2023 at 3:04 AM Fabrizio Castro
<fabrizio.castro.jz@...esas.com> wrote:
> "unsigned int" is more appropriate than "int" for the members
> of "struct rzv2m_csi_priv".

Agreed.

> Also, members "bytes_per_word" and "errors" introduce gaps
> in the structure.

While enlarging the types does get rid of the gaps, that was not the
intent of my comment ;-)
You can reorder fields to avoid gaps, and reduce the size of the structure.

> Adjust "struct rzv2m_csi_priv" and its members usage accordingly.
> While at it, remove the unnecessary casting of "data" to
> "struct rzv2m_csi_priv*" in function "rzv2m_csi_irq_handler".
>
> Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>

> --- a/drivers/spi/spi-rzv2m-csi.c
> +++ b/drivers/spi/spi-rzv2m-csi.c

> @@ -88,14 +88,14 @@ struct rzv2m_csi_priv {
>         struct spi_controller *controller;
>         const void *txbuf;
>         void *rxbuf;
> -       int buffer_len;
> -       int bytes_sent;
> -       int bytes_received;
> -       int bytes_to_transfer;
> -       int words_to_transfer;
> -       unsigned char bytes_per_word;
> +       unsigned int buffer_len;
> +       unsigned int bytes_sent;
> +       unsigned int bytes_received;
> +       unsigned int bytes_to_transfer;
> +       unsigned int words_to_transfer;
> +       unsigned int bytes_per_word;

bytes_per_word is calculated from spi_transfer.bits_per_word,
so u8 was fine.

>         wait_queue_head_t wait;
> -       u8 errors;
> +       u32 errors;

u8 was sufficiently large to hold all possible values.

>         u32 status;
>  };
>

Anyway, the code should work fine, so
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

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