Re: [PATCH v3 12/12] iio: dac: ad5686: add gain control support

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

On Tue, Jun 16, 2026 at 09:21:18AM +0100, Rodrigo Alencar via B4 Relay wrote:

> Most of the supported devices rely on a GAIN pin to control a 2x
> multiplier applied to the output voltage. Other devices, e.g. the
> single-channel ones, provides a gain control through a bit field in
> the control register. Some designs might have the GAIN pin hardwired
> to VDD/VLOGIC or GND, which would have no "gain-gpios" device property,
> being able to set "adi,range-double" if it is hardwired to VDD. The
> vref_mv field is moved down in the struct ad5686_state, so that the
> overall size increase is reduced.

...

> +static void ad5686_init_scale_avail(struct ad5686_state *st)
> +{
> +	int realbits = st->chip_info->channels[0].scan_type.realbits;
> +	s64 tmp = 2ULL * st->vref_mv * NANO >> realbits;

As Nuno noticed in other patch review, this can probably use mul_u64_u32_shr().

> +	st->scale_avail[2] = div_s64_rem(tmp, NANO, &st->scale_avail[3]);
> +	st->scale_avail[0] = div_s64_rem(tmp >> 1, NANO, &st->scale_avail[1]);
> +}

-- 
With Best Regards,
Andy Shevchenko