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In-Reply-To: <7d8ab7fee45222cdbaf80c507525f2d3941587c1.1675371372.git.christophe.jaillet@wanadoo.fr>
From:   Loic Poulain <loic.poulain@linaro.org>
Date:   Sun, 5 Feb 2023 14:18:07 +0100
Message-ID: <CAMZdPi-hUyorX6N-3koxOZ+gSxovdQc7iKxx7wuN+qJek_cvCA@mail.gmail.com>
Subject: Re: [PATCH net-next] wifi: wcn36xx: Slightly optimize PREPARE_HAL_BUF()
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc:     Kalle Valo <kvalo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org, wcn36xx@lists.infradead.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org
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On Thu, 2 Feb 2023 at 21:58, Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
> In most (likely all) cases, INIT_HAL_MSG() is called before
> PREPARE_HAL_BUF().
> In such cases calling memset() is useless because:
>    msg_body.header.len = sizeof(msg_body)
>
> So, instead of writing twice the memory, we just have a sanity check to
> make sure that some potential trailing memory is zeroed.
> It even gives the opportunity to see that by itself and optimize it away.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Acked-by: Loic Poulain <loic.poulain@linaro.org>


> ---
>  drivers/net/wireless/ath/wcn36xx/smd.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/wcn36xx/smd.c b/drivers/net/wireless/ath/wcn36xx/smd.c
> index 566f0b9c1584..17e1919d1cd8 100644
> --- a/drivers/net/wireless/ath/wcn36xx/smd.c
> +++ b/drivers/net/wireless/ath/wcn36xx/smd.c
> @@ -475,8 +475,8 @@ static int wcn36xx_smd_send_and_wait(struct wcn36xx *wcn, size_t len)
>
>  #define PREPARE_HAL_BUF(send_buf, msg_body) \
>         do {                                                    \
> -               memset(send_buf, 0, msg_body.header.len);       \
> -               memcpy(send_buf, &msg_body, sizeof(msg_body));  \
> +               memcpy_and_pad(send_buf, msg_body.header.len,   \
> +                              &msg_body, sizeof(msg_body), 0); \
>         } while (0)                                             \
>
>  #define PREPARE_HAL_PTT_MSG_BUF(send_buf, p_msg_body) \
> --
> 2.34.1
>