Re: [PATCH v5 3/4] iio: adc: ad799x: cache regulator voltages during probe

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Wed, Mar 18, 2026 at 02:57:14PM +0530, Archit Anant wrote:
> Reading the regulator voltage via regulator_get_voltage() can be a slow
> operation. Since the reference voltages for this ADC are not expected to
> change at runtime, it is inefficient to query the regulator API every
> time userspace reads the IIO_CHAN_INFO_SCALE attribute.
> 
> Determine the active reference voltage (either VREF or VCC) during
> probe() and cache it in the state structure. This improves the
> performance of ad799x_read_raw() and removes the dependency on the
> regulator pointers during fast-path reads.

...

>  	case IIO_CHAN_INFO_SCALE:
> -		if (st->vref)
> -			ret = regulator_get_voltage(st->vref);
> -		else
> -			ret = regulator_get_voltage(st->reg);
> -
> -		if (ret < 0)
> -			return ret;
> -		*val = ret / 1000;
> +		*val = st->vref_uV / MILLI;

Not sure I understand properly this MILLI in conjunction with FRACTIONAL_LOG2
below. Is this simply millivolts? Then we have "(MICRO / MILLI)" pattern as
of today to show that in a better way.

>  		*val2 = chan->scan_type.realbits;
>  		return IIO_VAL_FRACTIONAL_LOG2;

-- 
With Best Regards,
Andy Shevchenko