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

[Muhammad Usama Anjum]

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.