linux-kernel - Re: [PATCH 2/2] iio: adc: Add support for AD4000

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Date: Mon, 25 Mar 2024 08:35:16 -0500
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org, 
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, 
	marcelo.schmitt1@...il.com, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: adc: Add support for AD4000

On Sat, Mar 23, 2024 at 4:53 PM David Lechner <dlechner@...libre.com> wrote:
>
> On Fri, Mar 22, 2024 at 5:06 PM Marcelo Schmitt
> <marcelo.schmitt@...log.com> wrote:
> >

..

> > +
> > +       vref_reg = devm_regulator_get(&spi->dev, "vref");
>
> This should to be devm_regulator_get_optional(), otherwise it can
> return a "dummy" regulator if one is missing in the devicetree which
> will fail when getting the voltage.
>
> > +       if (IS_ERR(vref_reg))
> > +               return dev_err_probe(&spi->dev, PTR_ERR(vref_reg),
> > +                                    "Failed to get vref regulator\n");
> > +
> > +       ret = regulator_enable(vref_reg);
> > +       if (ret < 0)
> > +               return dev_err_probe(&spi->dev, ret,
> > +                                    "Failed to enable voltage regulator\n");
> > +
> > +       ret = devm_add_action_or_reset(&spi->dev, ad4000_regulator_disable, vref_reg);
> > +       if (ret)
> > +               return dev_err_probe(&spi->dev, ret,
> > +                                    "Failed to add regulator disable action\n");
> > +
> > +       st->vref = regulator_get_voltage(vref_reg);
> > +       if (st->vref < 0)
> > +               return dev_err_probe(&spi->dev, st->vref, "Failed to get vref\n");
> > +
> > +       if (!device_property_present(&spi->dev, "adi,spi-cs-mode")) {
> > +               st->cnv_gpio = devm_gpiod_get(&spi->dev, "cnv", GPIOD_OUT_HIGH);
> > +               if (IS_ERR(st->cnv_gpio)) {
> > +                       if (PTR_ERR(st->cnv_gpio) == -EPROBE_DEFER)
> > +                               return -EPROBE_DEFER;
> > +
> > +                       return dev_err_probe(&spi->dev, PTR_ERR(st->cnv_gpio),
> > +                                            "Failed to get CNV GPIO");
> > +               }
> > +       }
>

In a review for a different patch, Jonathan said he would prefer
devm_regulator_get() and failing in regulator_get_voltage() rather
than using devm_regulator_get_optional() so I think the same would
apply here and my suggestion should be overruled.