linux-kernel - Re: [PATCH] iio: use div64_u64() instead of do

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Date:   Sun, 13 Feb 2022 17:59:40 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Qing Wang <wangqing@...o.com>
Cc:     Jyoti Bhayana <jbhayana@...gle.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: use div64_u64() instead of do_div()

On Wed,  9 Feb 2022 00:37:53 -0800
Qing Wang <wangqing@...o.com> wrote:

> 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>
These look correct to me.  Jyoti, please could give these a sanity check?

Thanks,

Jonathan

> ---
>  drivers/iio/common/scmi_sensors/scmi_iio.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/common/scmi_sensors/scmi_iio.c b/drivers/iio/common/scmi_sensors/scmi_iio.c
> index d538bf3..d6df5da
> --- a/drivers/iio/common/scmi_sensors/scmi_iio.c
> +++ b/drivers/iio/common/scmi_sensors/scmi_iio.c
> @@ -160,7 +160,7 @@ static int scmi_iio_set_odr_val(struct iio_dev *iio_dev, int val, int val2)
>  	mult = scnprintf(buf, sizeof(buf), "%llu", sf) - 1;
>  
>  	sec = int_pow(10, mult) * UHZ_PER_HZ;
> -	do_div(sec, uHz);
> +	div64_u64(sec, uHz);
>  	if (sec == 0) {
>  		dev_err(&iio_dev->dev,
>  			"Trying to set invalid sensor update value for sensor %s",
> @@ -237,10 +237,10 @@ static void convert_ns_to_freq(u64 interval_ns, u64 *hz, u64 *uhz)
>  	u64 rem, freq;
>  
>  	freq = NSEC_PER_SEC;
> -	rem = do_div(freq, interval_ns);
> +	rem = div64_u64(freq, interval_ns);
>  	*hz = freq;
>  	*uhz = rem * 1000000UL;
> -	do_div(*uhz, interval_ns);
> +	div64_u64(*uhz, interval_ns);
>  }
>  
>  static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2)
> @@ -266,7 +266,7 @@ static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2)
>  	mult = SCMI_SENS_CFG_GET_UPDATE_EXP(sensor_config);
>  	if (mult < 0) {
>  		sensor_interval_mult = int_pow(10, abs(mult));
> -		do_div(sensor_update_interval, sensor_interval_mult);
> +		div64_u64(sensor_update_interval, sensor_interval_mult);
>  	} else {
>  		sensor_interval_mult = int_pow(10, mult);
>  		sensor_update_interval =
> @@ -500,7 +500,7 @@ static u64 scmi_iio_convert_interval_to_ns(u32 val)
>  	mult = SCMI_SENS_INTVL_GET_EXP(val);
>  	if (mult < 0) {
>  		sensor_interval_mult = int_pow(10, abs(mult));
> -		do_div(sensor_update_interval, sensor_interval_mult);
> +		div64_u64(sensor_update_interval, sensor_interval_mult);
>  	} else {
>  		sensor_interval_mult = int_pow(10, mult);
>  		sensor_update_interval =