netdev - Re: [PATCH] net: wireless: ath: use div64_u64() instead of do

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Message-ID: <877da2c3xf.fsf@tynnyri.adurom.net>
Date:   Thu, 10 Feb 2022 14:16:28 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Qing Wang <wangqing@...o.com>
Cc:     Maya Erez <merez@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, wil6210@....qualcomm.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: wireless: ath: use div64_u64() instead of do_div()

Qing Wang <wangqing@...o.com> writes:

> From: Wang Qing <wangqing@...o.com>
>
> do_div() does a 64-by-32 division.
> When the divisor is u64, do_div() truncates it to 32 bits, this means it
> can test non-zero and be truncated to zero for division.
>
> fix do_div.cocci warning:
> do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>
> Signed-off-by: Wang Qing <wangqing@...o.com>
> ---
>  drivers/net/wireless/ath/wil6210/debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/wil6210/debugfs.c b/drivers/net/wireless/ath/wil6210/debugfs.c
> index 4c944e5..2cee9dd
> --- a/drivers/net/wireless/ath/wil6210/debugfs.c
> +++ b/drivers/net/wireless/ath/wil6210/debugfs.c
> @@ -1766,7 +1766,7 @@ __acquires(&p->tid_rx_lock) __releases(&p->tid_rx_lock)
>  			seq_puts(s, "\n");
>  			if (!num_packets)
>  				continue;
> -			do_div(tx_latency_avg, num_packets);
> +			div64_u64(tx_latency_avg, num_packets);

As you have been pointed out in your other patches, do_div() and
div64_u64() work differently.

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