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

On 26/01/19 07:07PM, Andy Shevchenko wrote:

On Mon, Jan 19, 2026 at 04:37:09PM +0000, Rodrigo Alencar wrote:

quoted

On 26/01/19 03:42PM, Andy Shevchenko wrote:

quoted

On Mon, Jan 19, 2026 at 11:21:59AM +0000, Rodrigo Alencar wrote:

quoted

On 26/01/19 09:31AM, Andy Shevchenko wrote:

quoted

On Fri, Jan 16, 2026 at 02:32:22PM +0000, Rodrigo Alencar via B4 Relay wrote:

...

quoted

quoted

quoted

quoted

quoted

+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;

quoted

+		} else if (*str == '.' && !frac_part) {

This can be found by strchr() / strrchr() (depending on the expectations of
the input).

quoted

+			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).

quoted

+	for (; f_count > 0; f_count--)
+		uhz *= 10;

This is int_pow(10).

quoted

+	*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?

Correct, integer part of the frequency value goes up to 26.5 GHz
(uint_max is approx 4.3 GHz). Also, with the dual modulus, the PLL can
achieve micro Hz resolution.

Kind regards,

Rodrigo Alencar