Re: [PATCH] staging: iio: ad5933: Use div64_ul instead of do_div

Deepak R Varma
2022-10-31T10:06:29Z

On Sat, Oct 29, 2022 at 09:52:40AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Oct 28, 2022 at 02:58:49AM +0530, Deepak R Varma wrote:
> > do_div() does a 64-by-32 division. Here the divisor is an unsigned long
> > which on some platforms is 64 bit wide. So use div64_ul instead of do_div
> > to avoid a possible truncation. Issue was identified using the
> > coccicheck tool.
> >
> > Signed-off-by: Deepak R Varma <drv@mailo.com>
> > ---
> > drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> > index f177b20f0f2d..730bb31a20d8 100644
> > --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> > +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> > @@ -196,7 +196,7 @@ static int ad5933_set_freq(struct ad5933_state *st,
> > } dat;
> >
> > freqreg = (u64)freq * (u64)(1 << 27);
> > - do_div(freqreg, st->mclk_hz / 4);
> > + freqreg = div64_ul(freqreg, st->mclk_hz / 4);
> >
> > switch (reg) {
> > case AD5933_REG_FREQ_START:
> > --
> > 2.34.1
>
> No, this isn't ok, please read the mailing list archives for why these
> changes are not going to be accepted:
> https://lore.kernel.org/r/e2ec77060cc84a33b49d5fd11d7867f6@AcuMS.aculab.com
>
> Please always at least look at the archives of the past few weeks as to
> if changes like this are able to be accepted or not.

Hello Greg,
My apologies for not looking at the lore mailing archive. I only looked at the
past git commits and found a few similar changes accepted in the past. My bad. I
will always look at the mailing archive as well going forward.

There are other review comments from the experts on similar patches. I
appreciate everyone's time and comment. I will look at those and revert
accordingly.

Thank you,
./drv
>
> thanks,
>
> greg k-h