Re: [PATCH v4 3/7] iio: frequency: adf41513: driver implementation

Andy Shevchenko
2026-01-19T17:07:17Z

On Mon, Jan 19, 2026 at 04:37:09PM +0000, Rodrigo Alencar wrote:
> On 26/01/19 03:42PM, Andy Shevchenko wrote:
> > On Mon, Jan 19, 2026 at 11:21:59AM +0000, Rodrigo Alencar wrote:
> > > On 26/01/19 09:31AM, Andy Shevchenko wrote:
> > > > On Fri, Jan 16, 2026 at 02:32:22PM +0000, Rodrigo Alencar via B4 Relay wrote:

...

> > > > > +static int adf41513_parse_uhz(const char *str, u64 *freq_uhz)
> > > > > +{
> > > > > + u64 uhz = 0;
> > > > > + int f_count = ADF41513_HZ_DECIMAL_PRECISION;
> > > > > + bool frac_part = false;
> > > > > +
> > > > > + if (str[0] == '+')
> > > > > + str++;
> > > > > +
> > > > > + while (*str && f_count > 0) {
> > > > > + if ('0' <= *str && *str <= '9') {
> > > > > + uhz = uhz * 10 + *str - '0';
> > > > > + if (frac_part)
> > > > > + f_count--;
> > > > > + } else if (*str == '\n') {
> > > > > + if (*(str + 1) == '\0')
> > > > > + break;
> > > > > + return -EINVAL;
> > > >
> > > > > + } else if (*str == '.' && !frac_part) {
> > > >
> > > > This can be found by strchr() / strrchr() (depending on the expectations of
> > > > the input).
> > > >
> > > > > + frac_part = true;
> > > > > + } else {
> > > > > + return -EINVAL;
> > > > > + }
> > > > > + str++;
> > > > > + }
> > > >
> > > > With the above the rest becomes just a couple of simple_strtoull() calls with
> > > > a couple of int_pow(10) calls (and some validation on top).
> > > >
> > > > > + for (; f_count > 0; f_count--)
> > > > > + uhz *= 10;
> > > >
> > > > This is int_pow(10).
> > > >
> > > > > + *freq_uhz = uhz;
> > > > > +
> > > > > + return 0;
> > > > > +}
> > >
> > > The current implementation is kind of a stripped version of
> > > __iio_str_to_fixpoint(). Would you prefer something like this, then?:
> >
> > Do they have most of the parts in common? If so, why can't we use
> > __iio_str_to_fixpoint() directly? Or why can't we slightly refactor
> > that to give us the results we need here?
>
> __iio_str_to_fixpoint() only parses "int" chunks, adf41513_parse_uhz
> was modified to accomodate the u64 parsing removing unnecessary stuff.

But why? The fractional part most likely will be kept int (it's up to 10⁻⁹).
The integer can be bigger than 10⁹?

> I am preparing V5 to use simple_strtoull. Thanks for early review
> and suggestions.

--
With Best Regards,
Andy Shevchenko