Re: drivers/iio/common/scmi_sensors/scmi_iio.c:247:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.

[Geert Uytterhoeven]

CC IIO/SCMI

On Wed, 3 Jun 2026 at 20:36, kernel test robot <lkp@xxxxxxxxx> wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   ba3e43a9e601636f5edb54e259a74f96ca3b8fd8
> commit: a0e2cb6a90634f3dc80f16e882a683ee5761b0b0 um: Add VFIO-based virtual PCI driver
> date:   1 year, 1 month ago
> config: um-randconfig-r052-20260603 (https://download.01.org/0day-ci/archive/20260604/202606040245.XfmRpBhA-lkp@xxxxxxxxx/config)
> compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project e5ab4f8a1f766febdc65ce89c00dec85393cfd68)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Fixes: a0e2cb6a9063 ("um: Add VFIO-based virtual PCI driver")
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202606040245.XfmRpBhA-lkp@xxxxxxxxx/
>
> cocci warnings: (new ones prefixed by >>)
> >> drivers/iio/common/scmi_sensors/scmi_iio.c:247:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>    drivers/iio/common/scmi_sensors/scmi_iio.c:507:2-8: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>    drivers/iio/common/scmi_sensors/scmi_iio.c:273:2-8: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>    drivers/iio/common/scmi_sensors/scmi_iio.c:166:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>
> vim +247 drivers/iio/common/scmi_sensors/scmi_iio.c
>
> f774117c96f94c Jyoti Bhayana 2021-03-09  238
> f774117c96f94c Jyoti Bhayana 2021-03-09  239  static void convert_ns_to_freq(u64 interval_ns, u64 *hz, u64 *uhz)
> f774117c96f94c Jyoti Bhayana 2021-03-09  240  {
> f774117c96f94c Jyoti Bhayana 2021-03-09  241    u64 rem, freq;
> f774117c96f94c Jyoti Bhayana 2021-03-09  242
> f774117c96f94c Jyoti Bhayana 2021-03-09  243    freq = NSEC_PER_SEC;
> f774117c96f94c Jyoti Bhayana 2021-03-09  244    rem = do_div(freq, interval_ns);
> f774117c96f94c Jyoti Bhayana 2021-03-09  245    *hz = freq;
> f774117c96f94c Jyoti Bhayana 2021-03-09  246    *uhz = rem * 1000000UL;
> f774117c96f94c Jyoti Bhayana 2021-03-09 @247    do_div(*uhz, interval_ns);

Indeed, most do_div() use in that driver is broken on 32-bit.

> f774117c96f94c Jyoti Bhayana 2021-03-09  248  }
> f774117c96f94c Jyoti Bhayana 2021-03-09  249
>
> :::::: The code at line 247 was first introduced by commit
> :::::: f774117c96f94c7c4d2f076e4cacc80218b0df48 iio/scmi: Adding support for IIO SCMI Based Sensors
>
> :::::: TO: Jyoti Bhayana <jbhayana@xxxxxxxxxx>
> :::::: CC: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

So why was this sent to different people instead?

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds