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

Rodrigo Alencar
2026-01-19T16:37:21Z

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:

...
> > > > +struct adf41513_pll_settings {
> > > > + enum adf41513_pll_mode mode;
> > >
> > > Sounds to me like a room to improve the layout here,
> >
> > I am targeting a 32-bit cpu, just moved in_value down:
> > would this be fine? (pahole output):
>
> Likely.
>
> > struct adf41513_pll_settings {
> > enum adf41513_pll_mode mode; /* 0 4 */
>
> Wondering if this can be shorter if moved down...
>
> > u8 r_counter; /* 4 1 */
> > u8 ref_doubler; /* 5 1 */
> > u8 ref_div2; /* 6 1 */
> > u8 prescaler; /* 7 1 */
> > u64 target_frequency_uhz; /* 8 8 */
> > u64 actual_frequency_uhz; /* 16 8 */
> > u64 pfd_frequency_uhz; /* 24 8 */
> > u32 frac1; /* 32 4 */
> > u32 frac2; /* 36 4 */
> > u32 mod2; /* 40 4 */
> > u16 int_value; /* 44 2 */
> >
> > /* size: 48, cachelines: 1, members: 12 */
> > /* padding: 2 */
> > /* last cacheline: 48 bytes */
> > };
>
> ...at least I have had in mind that "mode" should be moved to be near
> to "int_value". But I think it will take 4 bytes still as we don't use
> short enums compile wise.
>

As you mentioned without short-enums it does not make any difference.

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

Kind regards,

Rodrigo Alencar