Re: [PATCH RFC v3 8/8] iio: ti-adc128s052: Drop variable vref

Jonathan Cameron
2025-04-12T11:42:37Z

On Fri, 11 Apr 2025 08:34:42 -0500
David Lechner <dlechner@baylibre.com> wrote:

> On 4/7/25 6:37 AM, Matti Vaittinen wrote:
> > According to Jonathan, variable reference voltages are very rare. It is
> > unlikely it is needed, and supporting it makes the code a bit more
> > complex.
> >
> > Simplify the driver and drop the variable vref support.
> >
> > Suggested-by: Jonathan Cameron <jic23@kernel.org>
> > Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> >
> > ---
>
> ...
>
> > static int adc128_probe(struct spi_device *spi)
> > {
> > const struct adc128_configuration *config;
> > @@ -183,17 +173,12 @@ static int adc128_probe(struct spi_device *spi)
> > indio_dev->channels = config->channels;
> > indio_dev->num_channels = config->num_channels;
> >
> > - adc->reg = devm_regulator_get(&spi->dev, config->refname);
> > - if (IS_ERR(adc->reg))
> > - return PTR_ERR(adc->reg);
> > + adc->vref_mv = devm_regulator_get_enable_read_voltage(&spi->dev,
> > + config->refname);
> > + if (adc->vref_mv < 0)
> > + return adc->vref_mv;
> >
> > - ret = regulator_enable(adc->reg);
> > - if (ret < 0)
> > - return ret;
> > - ret = devm_add_action_or_reset(&spi->dev, adc128_disable_regulator,
> > - adc->reg);
> > - if (ret)
> > - return ret;
> > + adc->vref_mv /= 1000;
>
> In other drivers, we've been doing:
>
> ret = devm_regulator_get_enable_read_voltage(...);
> if (ret < 0)
> return dev_err_probe(dev, ret, "failed to read '%s' voltage, ...);
>
> adc->vref_mv = ret / 1000;
>
> It can be easy to make a typo or forget to specify the voltage when creating
> a .dts, so I think the error message is helpful to catch that.
>
> And we use ret to avoid having adc->vref_mv temporarily holding a
> value with the wrong units (and can make it have an unsigned type).

Good idea.
Applied patches 1-7. I did tweak this one as well but then couldn't make
up my mind on whether to change the type of vref_mv so I'll avoid making
a decision and will leave patch 8 for a v4 from Matti :)

Jonathan

>
> >
> > if (config->num_other_regulators) {
> > ret = devm_regulator_bulk_get_enable(&spi->dev,
>