Hi!
On 2022-01-09 13:48, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@xxxxxxxxx> wrote:
>>
>> Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
>> Add support for these to allow using the iio-rescaler with them.
>
> ...
>
>> + mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
>> +
>> + /*
>> + * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
>> + * OR *val2 is negative the schan scale is negative, i.e.
>> + * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
>> + */
>> + neg = *val < 0 || *val2 < 0;
>> +
>> + tmp = (s64)abs(*val) * abs(rescale->numerator);
>> + *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
>> +
>> + tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
>> + tmp = div_s64(tmp, abs(rescale->denominator));
>
> Isn't it too many repetitive abs() calls?
>
> What about
>
> // Create a macro and use for u16 (struct rn5t618_channel_ratios), s16
> (struct twl4030_prescale_divider_ratios), s32 (can be reused in struct
> rescale)
> struct u32_fract {
> u32 numerator;
> u32 denominator;
> };
> // (potential reuse in struct hclge_ptp_cycle) and so on...
>
> struct u32_fract fract = {
> .numerator = abs(rescale->numerator),
> .denominator = abs(rescale->denominator),
> };
>
> // obviously we can add a macro/inliner to abs() the fract struct and
> return original sign
>
> and reuse fract.numerator, fract.denominator?
This feels a bit excessive when the "problem" is two extra abs calls.
I don't think the code will get any easier to read by changing
abs(rescale->denominator) into fract.denominator and with my maintainer
hat on, I vote for just letting the compiler exercise its CSE engine.
Cheers,
Peter
