linux-kernel - Re: [PATCH] staging: iio: Use div64_ul instead of do

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Date:   Thu, 20 Oct 2022 17:27:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Kang Minchul <tegongkang@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: iio: Use div64_ul instead of do_div

On Wed, Oct 19, 2022 at 02:38:29PM +0900, Kang Minchul wrote:
> Using div64_ul instead of do_div (64-by-32 division) is more
> recommended by coccicheck because this can avoid potential truncation.
> 
> So this commit changes do_div to div64_ul and
> remove coccicheck warnings.
> 
> Signed-off-by: Kang Minchul <tegongkang@...il.com>
> ---
>  drivers/staging/iio/frequency/ad9832.c          | 2 +-
>  drivers/staging/iio/frequency/ad9834.c          | 2 +-
>  drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> index 6f9eebd6c7ee..cd038480f63c 100644
> --- a/drivers/staging/iio/frequency/ad9832.c
> +++ b/drivers/staging/iio/frequency/ad9832.c
> @@ -122,7 +122,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout *
>  				     (u64)((u64)1L << AD9832_FREQ_BITS);
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);

I think the original code here is correct, no need for a change, unless
you have the hardware to test this out and can verify it all still works
identically.

thanks,

greg k-h