Re: [PATCH] iio: use div64_u64() instead of do_div()

[Christophe JAILLET]

Le 13/02/2022 à 19:50, Christophe JAILLET a écrit :
> Le 13/02/2022 à 18:59, Jonathan Cameron a écrit :
> > On Wed,  9 Feb 2022 00:37:53 -0800
> > Qing Wang <wangqing-DGpbCiVdSXo@xxxxxxxxxxxxxxxx> wrote:
> >
> > > From: Wang Qing <wangqing-DGpbCiVdSXo@xxxxxxxxxxxxxxxx>
> > >
> > > 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-DGpbCiVdSXo@xxxxxxxxxxxxxxxx>
> > These look correct to me.  Jyoti, please could give these a sanity check?
>
> This is wrong.
>
> See [1].
>
> CJ
>
> [1]: 
> https://lore.kernel.org/linux-kernel/20211117112559.jix3hmx7uwqmuryg-bIcnvbaLZ9MEGnE8C9+IrQ@xxxxxxxxxxxxxxxx/ 

Broken link, sorry:

[1] 
https://lore.kernel.org/linux-kernel/20211117112559.jix3hmx7uwqmuryg@xxxxxxxxxxxxxx/

> > 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 =