netdev - Re: [PATCH net-next] wifi: wcn36xx: Slightly optimize PREPARE_HAL

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Date:   Sun, 5 Feb 2023 14:18:07 +0100
From:   Loic Poulain <loic.poulain@...aro.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, wcn36xx@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] wifi: wcn36xx: Slightly optimize PREPARE_HAL_BUF()

On Thu, 2 Feb 2023 at 21:58, Christophe JAILLET
<christophe.jaillet@...adoo.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@...adoo.fr>

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