Re: [PATCH] drivers:iio:dac make expression evaluation 64-bit

[Lars-Peter Clausen]

On 12/23/21 5:34 PM, Muhammad Usama Anjum wrote:
> On 12/22/21 11:49 PM, Andy Shevchenko wrote:
> > On Wed, Dec 22, 2021 at 5:59 PM Muhammad Usama Anjum
> > <usama.anjum@xxxxxxxxxxxxx> wrote:
> > > Two 32-bit values are being evaluated using 32-bit arithmetic and then
> > > passed to s64 type. It is wrong. Expression should be evaluated using
> > > 64-bit arithmetic and then passed.
> > ...
> >
> > >          dac->ch_data[ch].scale_dec = DIV_ROUND_CLOSEST((s64)rem * 1000000,
> > >                                                          65536);
> > Shouldn't the above be fixed as well? Has anybody tried to compile on
> > 32-bit arch this?
> No, it correct already. In this case, rem is being typecasted to s64 and
> then multiplied with a 32-bit number, 1000000. Thus 64-bit arithmetic is
> being performed here.

What Andy means is that this needs to be DIV_S64_ROUND_CLOSEST() to work 
on 32-bit platforms. But it is clearly unrelated to your change and 
should be in its own patch.